Improve Router Hygiene to Protect Against Russian State-Sponsored Targeting

This joint cybersecurity advisory addresses ongoing Russian government-sponsored cyber activity targeting networking devices, particularly routers, across critical sectors including communications, defense industrial base, energy, financial services, government services, and healthcare. The advisory is being released by the United States National Security Agency (NSA), United States Cybersecurity and Infrastructure Security Agency (CISA), United States Federal Bureau of Investigation (FBI), United States Department of Defense Cyber Crime Center (DC3), Australian Signals Directorate’s Australian Cyber Security Centre (ASD’s ACSC), Canadian Centre for Cyber Security (Cyber Centre), New Zealand National Cyber Security Centre (NCSC-NZ), United Kingdom National Cyber Security Centre (NCSC-UK), and Czech Republic National Cyber and Information Security Agency (NÚKIB), along with Danish Defence Intelligence Service (DDIS), Estonian Foreign Intelligence Service (EFIS), Estonian Information System Authority (RIA), Finnish Defence Intelligence (FDI), Finnish Security and Intelligence Service (SUPO), French National Cybersecurity Agency (ANSSI), Italian External Intelligence and Security Agency (AISE), Italian Internal Intelligence and Security Agency (AISI), and The Military Counterintelligence Service of Poland (SKW).

Executive summary: Russian Federal Security Service (FSB) Center 16 cyber actors continue to exploit poorly configured and vulnerable networking devices worldwide, opportunistically compromising multiple critical infrastructure sector networks. This CSA builds on FBI’s Russian Government Cyber Actors Targeting Networking Devices, Critical Infrastructure Public Service Announcement of the decade-plus FSB Center 16 cyber activity by providing additional tactics, techniques, and procedures (TTPs) to enable defenders to more fully understand and counter the threat.

Targeting details: The Russian FSB Center 16 cyber actors primarily use scanning to identify poorly configured networking devices, primarily routers, for exploitation. The actors scan for Internet IP ranges with active Simple Network Management Protocol (SNMP) agents that accept common or default community strings for authentication [T1595.001, T1595.002]. These scans, run via proxies, consist of SNMP Set-Requests from a spoofed IP address [T1027] containing Object Identifiers (OIDs) that instruct the SNMP agent on poorly configured networking devices to [T1569, T1602.001, T1090]:

• Copy its configuration to a file, often called “config.bkp” or “output.txt” [T1003, T1602.002].
• Transfer the file, typically using Trivial File Transfer Protocol (TFTP), to an actor-controlled leased virtual private server (VPS) or compromised FTP server [T1583.003, T1090, T1071, T1048].

While SNMP scanning is the primary method the actors use to discover and exploit poorly configured networking devices, they occasionally exploit common vulnerabilities and exposures (CVEs) in Cisco devices, Cisco’s Smart Install (SMI) functionality, and web portals to manage network devices. The actors previously exploited at least the following CVEs [T1584.008, T1588.005, T1190, T1068].

Many of these TTPs overlap with activity by other malicious cyber actors, such as Salt Typhoon. Even though this CSA focuses on Russian FSB Center 16 cyber activity, the mitigations below should detect and counter these and similar TTPs used by other actors.

Mitigation actions: The authoring agencies highly recommend network defenders implement the following mitigations to harden networks against this exploitation:

• Disable Cisco Smart Install on all devices [D3-ACH]. [2]
• Use SNMPv3 with “authPriv” configured to the most modern encryption standard that is supported by the device instead of SNMPv1 or SNMPv2 [D3-ACH]. [3]
• Disable SNMPv1 and SNMPv2. These are legacy protocols and should no longer be needed on current devices. If they are necessary, change all community strings from defaults and only allow read-only community strings rather than read-write access.
• SNMPv3 adds strong authentication and data encryption that are unavailable in SNMPv1 and v2. SNMPv3 replaces clear text shared passwords, known as community strings, with more securely encoded parameters, and authenticates and encrypts data [D3-MAN, D3-MENCR].
• Use strong, unique passwords for local accounts on network devices and configure credentials to be stored securely to prevent reuse of compromised passwords [D3-CH]. [4]
• Cisco devices protect passwords in the configuration file using different hashing types. Use hashing type 8 for user credentials. Avoid using hashing type 0, 4, and 7 as they are insecure or store passwords in plaintext in the configuration file. [5]
• Monitor for unusual credentials that do not conform to standard organizational naming conventions [D3-PM].
• Monitor and alert on logins using local accounts. Local accounts should only be used in emergency situations when accounts supported by centralized authentication servers are unavailable. Centralized authentication to network devices should support multi-factor authentication where feasible. [3]
• Monitor and restrict access to SNMP OIDs using a Management Information Base (MIB) allow list [D3-ACH]. [6]
• Reference the vendor-specific MIB for the network devices and monitor OIDs for indications of reconnaissance or misconfiguration in logs or intrusion detection systems (IDS). IDS rules should be written for inbound SNMP Set-Requests that contain OIDs targeting sensitive device data [D3-PM].
• Example OIDs include:
• 1.3.6.1.4.1.9.9.96.1.1 (Cisco Config Copy)
• 1.3.6.1.4.1.9.9.96.1.1.1.1.5 (Config Copy Server Address, value for this OID is where the configuration file is being sent to)

• Restrict management protocols [D3-NTF].
• Use Access Control Lists (ACLs) to only allow management protocols, such as SNMP, from management devices, preferably on an out-of-band network. [3]
• On edge firewalls and devices deny all external communications on the following ports unless mission critical, with strict monitoring if blocking is not feasible:
• User Datagram Protocol (UDP) port 69 (TFTP)
• Transmission Control Protocol (TCP) port 4786 (SMI)
• UDP ports 161 and 162 (SNMP)
• TCP/UDP ports 10161 and 10162 (SNMPv3)
• Update network device software and firmware images, especially to patch known vulnerabilities, and upgrade end-of-life devices to supported ones. Use an attack surface management service to identify and secure Internet-facing systems with weak configurations and known vulnerabilities [D3-NVA].
• U.S.-based federal, state, local, tribal, and territorial governments and U.S. critical infrastructure organizations should consider signing up for CISA’s no-cost Cyber Hygiene services. U.S. Defense Industrial Base organizations should consider signing up for NSA’s DIB Cybersecurity Services.
• Use an attack surface management service to identify and secure Internet-facing systems with weak configurations and known vulnerabilities [D3-NVA].

Resources: (Links to relevant documentation and resources would be included here).