US-CERT Security Alerts

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Alerts warn about vulnerabilities, incidents, and other security issues that pose a significant risk.
Updated: 1 hour 24 min ago

AA19-024A: DNS Infrastructure Hijacking Campaign

Thu, 01/24/2019 - 12:01
Original release date: January 24, 2019 | Last revised: February 13, 2019
Summary

The National Cybersecurity and Communications Integration Center (NCCIC), part of the Cybersecurity and Infrastructure Security Agency (CISA), is aware of a global Domain Name System (DNS) infrastructure hijacking campaign. Using compromised credentials, an attacker can modify the location to which an organization’s domain name resources resolve. This enables the attacker to redirect user traffic to attacker-controlled infrastructure and obtain valid encryption certificates for an organization’s domain names, enabling man-in-the-middle attacks.

See the following links for downloadable copies of open-source indicators of compromise (IOCs) from the sources listed in the References section below:

Note: these files were last updated February 13, 2019, to remove the following three non-malicious IP addresses:

  • 107.161.23.204
  • 192.161.187.200
  • 209.141.38.71
Technical Details

Using the following techniques, attackers have redirected and intercepted web and mail traffic, and could do so for other networked services.

  1. The attacker begins by compromising user credentials, or obtaining them through alternate means, of an account that can make changes to DNS records.
  2. Next, the attacker alters DNS records, like Address (A), Mail Exchanger (MX), or Name Server (NS) records, replacing the legitimate address of a service with an address the attacker controls. This enables them to direct user traffic to their own infrastructure for manipulation or inspection before passing it on to the legitimate service, should they choose. This creates a risk that persists beyond the period of traffic redirection.
  3. Because the attacker can set DNS record values, they can also obtain valid encryption certificates for an organization’s domain names. This allows the redirected traffic to be decrypted, exposing any user-submitted data. Since the certificate is valid for the domain, end users receive no error warnings.
Mitigations

NCCIC recommends the following best practices to help safeguard networks against this threat:

  • Update the passwords for all accounts that can change organizations’ DNS records.
  • Implement multifactor authentication on domain registrar accounts, or on other systems used to modify DNS records.
  • Audit public DNS records to verify they are resolving to the intended location.
  • Search for encryption certificates related to domains and revoke any fraudulently requested certificates.
References Revisions
  • January 24, 2019: Initial version
  • February 6, 2019: Updated IOCs, added Crowdstrike blog
  • February 13, 2019: Updated IOCs

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Categories: Security Alerts

AA18-337A: SamSam Ransomware

Mon, 12/03/2018 - 08:18
Original release date: December 03, 2018
Summary

The Department of Homeland Security (DHS) National Cybersecurity and Communications Integration Center (NCCIC) and the Federal Bureau of Investigation (FBI) are issuing this activity alert to inform computer network defenders about SamSam ransomware, also known as MSIL/Samas.A. Specifically, this product shares analysis of vulnerabilities that cyber actors exploited to deploy this ransomware. In addition, this report provides recommendations for prevention and mitigation.

The SamSam actors targeted multiple industries, including some within critical infrastructure. Victims were located predominately in the United States, but also internationally. Network-wide infections against organizations are far more likely to garner large ransom payments than infections of individual systems. Organizations that provide essential functions have a critical need to resume operations quickly and are more likely to pay larger ransoms.

The actors exploit Windows servers to gain persistent access to a victim’s network and infect all reachable hosts. According to reporting from victims in early 2016, cyber actors used the JexBoss Exploit Kit to access vulnerable JBoss applications. Since mid-2016, FBI analysis of victims’ machines indicates that cyber actors use Remote Desktop Protocol (RDP) to gain persistent access to victims’ networks. Typically, actors either use brute force attacks or stolen login credentials. Detecting RDP intrusions can be challenging because the malware enters through an approved access point.

After gaining access to a particular network, the SamSam actors escalate privileges for administrator rights, drop malware onto the server, and run an executable file, all without victims’ action or authorization. While many ransomware campaigns rely on a victim completing an action, such as opening an email or visiting a compromised website, RDP allows cyber actors to infect victims with minimal detection.

Analysis of tools found on victims’ networks indicated that successful cyber actors purchased several of the stolen RDP credentials from known darknet marketplaces. FBI analysis of victims’ access logs revealed that the SamSam actors can infect a network within hours of purchasing the credentials. While remediating infected systems, several victims found suspicious activity on their networks unrelated to SamSam. This activity is a possible indicator that the victims’ credentials were stolen, sold on the darknet, and used for other illegal activity.

SamSam actors leave ransom notes on encrypted computers. These instructions direct victims to establish contact through a Tor hidden service site. After paying the ransom in Bitcoin and establishing contact, victims usually receive links to download cryptographic keys and tools to decrypt their network.

Technical Details

NCCIC recommends organizations review the following SamSam Malware Analysis Reports. The reports represent four SamSam malware variants. This is not an exhaustive list.

For general information on ransomware, see the NCCIC Security Publication at https://www.us-cert.gov/security-publications/Ransomware.

Mitigations

DHS and FBI recommend that users and administrators consider using the following best practices to strengthen the security posture of their organization's systems. System owners and administrators should review any configuration changes before implementation to avoid unwanted impacts.

  • Audit your network for systems that use RDP for remote communication. Disable the service if unneeded or install available patches. Users may need to work with their technology venders to confirm that patches will not affect system processes.
  • Verify that all cloud-based virtual machine instances with public IPs have no open RDP ports, especially port 3389, unless there is a valid business reason to keep open RDP ports. Place any system with an open RDP port behind a firewall and require users to use a virtual private network (VPN) to access that system.
  • Enable strong passwords and account lockout policies to defend against brute force attacks.
  • Where possible, apply two-factor authentication.
  • Regularly apply system and software updates.
  • Maintain a good back-up strategy.
  • Enable logging and ensure that logging mechanisms capture RDP logins. Keep logs for a minimum of 90 days and review them regularly to detect intrusion attempts.
  • When creating cloud-based virtual machines, adhere to the cloud provider’s best practices for remote access.
  • Ensure that third parties that require RDP access follow internal policies on remote access.
  • Minimize network exposure for all control system devices. Where possible, disable RDP on critical devices.
  • Regulate and limit external-to-internal RDP connections. When external access to internal resources is required, use secure methods such as VPNs. Of course, VPNs are only as secure as the connected devices.
  • Restrict users' ability (permissions) to install and run unwanted software applications.
  • Scan for and remove suspicious email attachments; ensure the scanned attachment is its "true file type" (i.e., the extension matches the file header).
  • Disable file and printer sharing services. If these services are required, use strong passwords or Active Directory authentication.

Additional information on malware incident prevention and handling can be found in Special Publication 800-83, Guide to Malware Incident Prevention and Handling for Desktops and Laptops, from the National Institute of Standards and Technology.[1]

Contact Information

To report an intrusion and request resources for incident response or technical assistance, contact NCCIC, FBI, or the FBI’s Cyber Division via the following information:

Feedback

DHS strives to make this report a valuable tool for our partners and welcomes feedback on how this publication could be improved. You can help by answering a few short questions about this report at the following URL: https://www.us-cert.gov/forms/feedback.

References Revisions
  • December 3, 2018: Initial version

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Categories: Security Alerts

TA18-331A: 3ve – Major Online Ad Fraud Operation

Tue, 11/27/2018 - 09:09
Original release date: November 27, 2018
Systems Affected

Microsoft Windows

Overview

This joint Technical Alert (TA) is the result of analytic efforts between the Department of Homeland Security (DHS) and the Federal Bureau of Investigation (FBI). DHS and FBI are releasing this TA to provide information about a major online ad fraud operation—referred to by the U.S. Government as "3ve"—involving the control of over 1.7 million unique Internet Protocol (IP) addresses globally, when sampled over a 10-day window.

Description

Online advertisers desire premium websites on which to publish their ads and large numbers of visitors to view those ads. 3ve created fake versions of both (websites and visitors), and funneled the advertising revenue to cyber criminals. 3ve obtained control over 1.7 million unique IPs by leveraging victim computers infected with Boaxxe/Miuref and Kovter malware, as well as Border Gateway Protocol-hijacked IP addresses. 

Boaxxe/Miuref Malware

Boaxxe malware is spread through email attachments and drive-by downloads. The ad fraud scheme that utilizes the Boaxxe botnet is primarily located in a data center. Hundreds of machines in this data center are browsing to counterfeit websites. When these counterfeit webpages are loaded into a browser, requests are made for ads to be placed on these pages. The machines in the data center use the Boaxxe botnet as a proxy to make requests for these ads. A command and control (C2) server sends instructions to the infected botnet computers to make the ad requests in an effort to hide their true data center IPs.

Kovter Malware

Kovter malware is also spread through email attachments and drive-by downloads. The ad fraud scheme that utilizes the Kovter botnet runs a hidden Chromium Embedded Framework (CEF) browser on the infected machine that the user cannot see. A C2 server tells the infected machine to visit counterfeit websites. When the counterfeit webpage is loaded in the hidden browser, requests are made for ads to be placed on these counterfeit pages. The infected machine receives the ads and loads them into the hidden browser.

Impact

For the indicators of compromise (IOCs) below, keep in mind that any one indicator on its own may not necessarily mean that a machine is infected. Some IOCs may be present for legitimate applications and network traffic as well, but are included here for completeness.

Boaxxe/Miuref Malware

Boaxxe malware leaves several executables on the infected machine. They may be found in one or more of the following locations:

  • %UserProfile%\AppData\Local\VirtualStore\lsass.aaa
  • %UserProfile%\AppData\Local\Temp\<RANDOM>.exe
  • %UserProfile%\AppData\Local\<Random eight-character folder name>\<original file name>.exe

The HKEY_CURRENT_USER (HKCU) “Run” key is set to the path to one of the executables created above.

  • HKCU\Software\Microsoft\Windows\CurrentVersion\Run\<Above path to executable>\
Kovter Malware

Kovter malware is found mostly in the registry, but the following files may be found on the infected machine:

  • %UserProfile\AppData\Local\Temp\<RANDOM> .exe/.bat
  • %UserProfile%\AppData\Local\Microsoft\Windows\Temporary Internet Files\Content.IE5\<RANDOM>\<RANDOM FILENAME>.exe
  • %UserProfile%\AppData\Local\<RANDOM>\<RANDOM>.lnk
  • %UserProfile%\AppData\Local\<RANDOM>\<RANDOM>.bat

Kovter is known to hide in the registry under:

  • HKCU\SOFTWARE\<RANDOM>\<RANDOM>

The customized CEF browser is dropped to:

  • %UserProfile%\AppData\Local\<RANDOM>

The keys will look like random values and contain scripts. In some values, a User-Agent string can be clearly identified. An additional key containing a link to a batch script on the hard drive may be placed within registry key:

  • HKCU\SOFTWARE\Microsoft\Windows\CurrentVersion\Run

There are several patterns in the network requests that are made by Kovter malware when visiting the counterfeit websites. The following are regex rules for these URL patterns:

  • /?ptrackp=\d{5,8}
  • /feedrs\d/click?feed_id=\d{1,5}&sub_id=\d{1,5}&cid=[a-f0-9-]*&spoof_domain=[\w\.\d-_]*&land_ip=\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}
  • /feedrs\d/vast_track?a=impression&feed_id=\d{5}&sub_id=\d{1,5}&sub2_id=\d{1,5}&cid=[a-f\d-]

The following is a YARA rule for detecting Kovter:

rule KovterUnpacked {
  meta:
    desc = "Encoded strings in unpacked Kovter samples."
  strings:
    $ = "7562@3B45E129B93"
    $ = "@ouhKndCny"
    $ = "@ouh@mmEdctffdsr"
    $ = "@ouhSGQ"
  condition:
    all of them
}

Solution

If you believe you may be a victim of 3ve and its associated malware or hijacked IPs, and have information that may be useful to investigators, submit your complaint to www.ic3.gov and use the hashtag 3ve (#3ve) in the body of your complaint.

DHS and FBI advise users to take the following actions to remediate malware infections associated with Boaxxe/Miuref or Kovter:

  • Use and maintain antivirus software. Antivirus software recognizes and protects your computer against most known viruses. Security companies are continuously updating their software to counter these advanced threats. Therefore, it is important to keep your antivirus software up-to-date. If you suspect you may be a victim of malware, update your antivirus software definitions and run a full-system scan. (See Understanding Anti-Virus Software for more information.)
  • Avoid clicking links in email. Attackers have become very skilled at making phishing emails look legitimate. Users should ensure the link is legitimate by typing the link into a new browser. (See Avoiding Social Engineering and Phishing Attacks.)
  • Change your passwords. Your original passwords may have been compromised during the infection, so you should change them. (See Choosing and Protecting Passwords.)
  • Keep your operating system and application software up-to-date. Install software patches so that attackers cannot take advantage of known problems or vulnerabilities. You should enable automatic updates of the operating system if this option is available. (See Understanding Patches and Software Updates for more information.)
  • Use anti-malware tools. Using a legitimate program that identifies and removes malware can help eliminate an infection. Users can consider employing a remediation tool. A non-exhaustive list of examples is provided below. The U.S. Government does not endorse or support any particular product or vendor.
References Revision History
  • November 27, 2018: Initial version

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Categories: Security Alerts