Multiple vulnerabilities used in attack against routers

Severity: Medium
Dispersion:
Operating System: Generic Routing Encapsulation (GRE) Enabled Devices

Cisco Smart Install (SMI) Enabled Devices

Simple Network Management Protoctol (SNMP) Enabled Network Devices

Category: Vulnerabilities
Sources: US-Cert, Wired

 

From Alert

Multiple vulnerabilities used in massive state sponsored attacks. DHS has issued a statement claiming massive attacks against routers all over the world. This is been leveraged using the recently discovered Cisco SmartInstall feature on Cisco devices and 3 other vulnerabilities (Default password, SNMP and GRE). We urge all our customers to check the complete alert listing for more information on our webpage

Description

State-sponsored cyber actors is targeting network infrastructure devices. Leveraging a number of legacy or weak protocols and service ports associated with network administration activities. Cyber actors use these weaknesses to:
  • identify vulnerable devices;
  • extract device configurations;
  • map internal network architectures;
  • harvest login credentials;
  • masquerade as privileged users;
  • modify
    • device firmware,
    • operating systems,
    • configurations; and
  • copy or redirect victim traffic through Russian cyber-actor-controlled infrastructure.

Additionally, Cyber actors could potentially modify or deny traffic traversing through the router.

Cyber actors do not need to leverage zero-day vulnerabilities or install malware to exploit these devices. Instead, cyber actors take advantage of the following vulnerabilities:

  • devices with legacy unencrypted protocols or unauthenticated services,
  • devices insufficiently hardened before installation, and
  • devices no longer supported with security patches by manufacturers or vendors (end-of-life devices).

 

 

 

Recommended actions

Telnet

Review network device logs and netflow data for indications of TCP Telnet-protocol traffic directed at port 23 on all network device hosts. Although Telnet may be directed at other ports (e.g., port 80, HTTP), port 23 is the primary target. Inspect any indication of Telnet sessions (or attempts). Because Telnet is an unencrypted protocol, session traffic will reveal command line interface (CLI) command sequences appropriate for the make and model of the device. CLI strings may reveal login procedures, presentation of user credentials, commands to display boot or running configuration, copying files and creation or destruction of GRE tunnels, etc. See Appendices A and B for CLI strings for Cisco and other vendors’ devices.

SNMP and TFTP

Review network device logs and netflow data for indications of UDP SNMP traffic directed at port 161/162 on all network-device hosts. Because SNMP is a management tool, any such traffic that is not from a trusted management host on an internal network should be investigated. Review the source address of SNMP traffic for indications of addresses that spoof the address space of the network. Review outbound network traffic from the network device for evidence of Internet-destined UDP TFTP traffic. Any correlation of inbound or spoofed SNMP closely followed by outbound TFTP should be cause for alarm and further inspection. See Appendix C for detection of the cyber actors’ SNMP tactics.

Because TFTP is an unencrypted protocol, session traffic will reveal strings associated with configuration data appropriate for the make and model of the device. See Appendices A and B for CLI strings for Cisco and other vendor’s devices.

SMI and TFTP

Review network device logs and netflow data for indications of TCP SMI protocol traffic directed at port 4786 of all network-device hosts. Because SMI is a management feature, any traffic that is not from a trusted management host on an internal network should be investigated. Review outbound network traffic from the network device for evidence of Internet-destined UDP TFTP traffic. Any correlation of inbound SMI closely followed by outbound TFTP should be cause for alarm and further inspection. Of note, between June 29 and July 6, 2017, Russian actors used the SMI protocol to scan for vulnerable network devices. Two Russian cyber actors controlled hosts 91.207.57.69(3) and 176.223.111.160(4), and connected to IPs on several network ranges on port 4786. See Appendix D for detection of the cyber actors’ SMI tactics.

Because TFTP is an unencrypted protocol, session traffic will reveal strings appropriate for the make and model of the device. See Appendices A and B for CLI strings for Cisco and other vendors’ devices.

Determine if SMI is present

  • Examine the output of “show vstack config | inc Role”. The presence of “Role: Client (SmartInstall enabled)” indicates that Smart Install is configured.
  • Examine the output of “show tcp brief all” and look for “*:4786”. The SMI feature listens on tcp/4786.
  • Note: The commands above will indicate whether the feature is enabled on the device but not whether a device has been compromised.

Detect use of SMI

The following signature may be used to detect SMI usage. Flag as suspicious and investigate SMI traffic arriving from outside the network boundary. If SMI is not used inside the network, any SMI traffic arriving on an internal interface should be flagged as suspicious and investigated for the existence of an unauthorized SMI director. If SMI is used inside the network, ensure that the traffic is coming from an authorized SMI director, and not from a bogus director.

  • alert tcp any any -> any 4786 (msg:”Smart Install Protocol”; flow:established,only_stream; content:”|00 00 00 01 00 00 00 01|”; offset:0; depth:8; fast_pattern;)
  • See Cisco recommendations for detecting and mitigating SMI. [9](link is external)

Detect use of SIET

The following signatures detect usage of the SIET’s commands change_config, get_config, update_ios, and execute. These signatures are valid based on the SIET tool available as of early September 2017:

  • alert tcp any any -> any 4786 (msg:”SmartInstallExploitationTool_UpdateIos_And_Execute”; flow:established; content:”|00 00 00 01 00 00 00 01 00 00 00 02 00 00 01 c4|”; offset:0; depth:16; fast_pattern; content:”://”;)
  • alert tcp any any -> any 4786 (msg:”SmartInstallExploitationTool_ChangeConfig”; flow:established; content:”|00 00 00 01 00 00 00 01 00 00 00 03 00 00 01 28|”; offset:0; depth:16; fast_pattern; content:”://”;)
  • alert tcp any any -> any 4786 (msg: “SmartInstallExploitationTool_GetConfig”; flow: established; content:”|00 00 00 01 00 00 00 01 00 00 00 08 00 00 04 08|”; offset:0; depth:16; fast_pattern; content:”copy|20|”;)

In general, exploitation attempts with the SIET tool will likely arrive from outside the network boundary. However, before attempting to tune or limit the range of these signatures, i.e. with $EXTERNAL_NET or $HOME_NET, it is recommended that they be deployed with the source and destination address ranges set to “any”. This will allow the possibility of detection of an attack from an unanticipated source, and may allow for coverage of devices outside of the normal scope of what may be defined as the $HOME_NET.

GRE Tunneling

Inspect the presence of protocol 47 traffic flowing to or from unexpected addresses, or unexplained presence of GRE tunnel creation, modification, or destruction in log files.

 

More information and reference:

https://www.us-cert.gov/ncas/alerts/TA18-106A

https://www.wired.com/story/white-house-warns-russian-router-hacking-muddles-message/

 

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