Joint Cybersecurity Advisory: Russian State-Sponsored Cyber Actors Gain Network Access by Exploiting Default Multifactor Authentication Protocols

SUMMARY

The Federal Bureau of Investigation (FBI) and Cybersecurity and Infrastructure Security Agency (CISA) are releasing this joint Cybersecurity Advisory (CSA) to warn organizations that Russian state-sponsored cyber actors have gained network access through exploitation of default MFA protocols and a known vulnerability. As early as May 2021, Russian state-sponsored cyber actors took advantage of a misconfigured account set to default MFA protocols at a non-governmental organization (NGO), allowing them to enroll a new device for MFA and access the victim network. The actors then exploited a critical Windows Print Spooler vulnerability, “PrintNightmare” (CVE-2021-34527) to run arbitrary code with system privileges. Russian state-sponsored cyber actors successfully exploited the vulnerability while targeting an NGO using Cisco’s Duo MFA, enabling access to cloud and email accounts for document exfiltration.

This advisory provides observed tactics, techniques, and procedures, indicators of compromise (IOCs), and recommendations to protect against Russian state-sponsored malicious cyber activity.

FBI and CISA urge all organizations to apply the recommendations in the Mitigations section of this advisory, including the following:

• Enforce MFA and review configuration policies to protect against “fail open” and re-enrollment scenarios.
• Ensure inactive accounts are disabled uniformly across the Active Directory and MFA systems.
• Patch all systems. Prioritize patching for known exploited vulnerabilities.

For more general information on Russian state-sponsored malicious cyber activity, see CISA's Russia Cyber Threat Overview and Advisories webpage. For more information on the threat of Russian state-sponsored malicious cyber actors to U.S. critical infrastructure as well as additional mitigation recommendations, see joint CSA Understanding and Mitigating Russian State-Sponsored Cyber Threats to U.S. Critical Infrastructure and CISA’s Shields Up Technical Guidance webpage.

For a downloadable copy of IOCs, see AA22-074A.stix.

TECHNICAL DETAILS

Threat Actor Activity

Note: This advisory uses the MITRE ATT&CK® for Enterprise framework, version 10. See appendix A for a table of the threat actors’ activity mapped to MITRE ATT&CK tactics and techniques.

As early as May 2021, the FBI observed Russian state-sponsored cyber actors gain access to an NGO, exploit a flaw in default MFA protocols, and move laterally to the NGO’s cloud environment.

Russian state-sponsored cyber actors gained initial access [TA0001] to the victim organization via compromised credentials [T1078] and enrolling a new device in the organization’s Duo MFA. The actors gained the credentials [TA0006] via brute-force password guessing attack [T1110.001], allowing them access to a victim account with a simple, predictable password. The victim account had been un-enrolled from Duo due to a long period of inactivity but was not disabled in the Active Directory. As Duo’s default configuration settings allow for the re-enrollment of a new device for dormant accounts, the actors were able to enroll a new device for this account, complete the authentication requirements, and obtain access to the victim network.

Using the compromised account, Russian state-sponsored cyber actors performed privilege escalation [TA0004] via exploitation of the “PrintNightmare” vulnerability (CVE-2021-34527) [T1068] to obtain administrator privileges. The actors also modified a domain controller file, c:\windows\system32\drivers\etc\hosts, redirecting Duo MFA calls to localhost instead of the Duo server [T1556]. This change prevented the MFA service from contacting its server to validate MFA login—this effectively disabled MFA for active domain accounts because the default policy of Duo for Windows is to “fail open” if the MFA server is unreachable. Note: “Fail open” can happen to any MFA implementation and is not exclusive to Duo.

After effectively disabling MFA, Russian state-sponsored cyber actors were able to successfully authenticate to the victim’s virtual private network (VPN) as non-administrator users and make Remote Desktop Protocol (RDP) connections to Windows domain controllers [T1133]. The actors ran commands to obtain credentials for additional domain accounts; then, using the method described in the previous paragraph, changed the MFA configuration file and bypassed MFA for these newly compromised accounts. The actors leveraged mostly internal Windows utilities already present within the victim network to perform this activity.

Using these compromised accounts without MFA enforced, Russian state-sponsored cyber actors were able to move laterally [TA0008] to the victim’s cloud storage and email accounts and access desired content.

Indicators of Compromise

Russian state-sponsored cyber actors executed the following processes:

• ping.exe − A core Windows Operating System process used to perform the Transmission Control Protocol (TCP)/IP Ping command; used to test network connectivity to a remote host [T1018] and is frequently used by actors for network discovery [TA0007].
• regedit.exe − A standard Windows executable file that opens the built-in registry editor [T1112].
• rar.exe − A data compression, encryption, and archiving tool [T1560.001]. Malicious cyber actors have traditionally sought to compromise MFA security protocols as doing so would provide access to accounts or information of interest.
• ntdsutil.exe − A command-line tool that provides management facilities for Active Directory Domain Services. It is possible this tool was used to enumerate Active Directory user accounts [T1003.003].

Actors modified the c:\windows\system32\drivers\etc\hosts file to prevent communication with the Duo MFA server:

• 127.0.0.1 api-<redacted>.duosecurity.com

The following access device IP addresses used by the actors have been identified to date:

• 45.32.137[.]94
• 191.96.121[.]162
• 173.239.198[.]46
• 157.230.81[.]39

View the detailed report below.