SSH Authorized Keys File Modification

Elastic Stack Serverless Security

The Secure Shell (SSH) authorized_keys file specifies which users are allowed to log into a server using public key authentication. Adversaries may modify it to maintain persistence on a victim host by adding their own public key(s).

Rule type: query

Rule indices:

• auditbeat-*
• logs-endpoint.events.*

Severity: medium

Risk score: 47

Runs every: 5m

Searches indices from: now-9m (https://www.elastic.co/guide/en/elasticsearch/reference/current/common-options.html#date-math[Date Math format], see also Additional look-back time)

Maximum alerts per execution: 100

References: None

Tags:

• Elastic
• Host
• Linux
• macOS
• Threat Detection
• Lateral Movement
• Persistence

Version: 102

Rule authors:

• Elastic

Rule license: Elastic License v2

event.category:file and event.type:(change or creation) and
 file.name:("authorized_keys" or "authorized_keys2" or "/etc/ssh/sshd_config" or "/root/.ssh") and
 not process.executable:
             (/Library/Developer/CommandLineTools/usr/bin/git or
              /usr/local/Cellar/maven/*/libexec/bin/mvn or
              /Library/Java/JavaVirtualMachines/jdk*.jdk/Contents/Home/bin/java or
              /usr/bin/vim or
              /usr/local/Cellar/coreutils/*/bin/gcat or
              /usr/bin/bsdtar or
              /usr/bin/nautilus or
              /usr/bin/scp or
              /usr/bin/touch or
              /var/lib/docker/* or
              /usr/bin/google_guest_agent or
              /opt/jc/bin/jumpcloud-agent)

Framework: MITRE ATT&CKTM

• Tactic:

  • Name: Persistence
  • ID: TA0003
  • Reference URL: https://attack.mitre.org/tactics/TA0003/

• Technique:

  • Name: Account Manipulation
  • ID: T1098
  • Reference URL: https://attack.mitre.org/techniques/T1098/

• Sub-technique:

  • Name: SSH Authorized Keys
  • ID: T1098.004
  • Reference URL: https://attack.mitre.org/techniques/T1098/004/

• Tactic:

  • Name: Lateral Movement
  • ID: TA0008
  • Reference URL: https://attack.mitre.org/tactics/TA0008/

• Technique:

  • Name: Remote Service Session Hijacking
  • ID: T1563
  • Reference URL: https://attack.mitre.org/techniques/T1563/

• Sub-technique:

  • Name: SSH Hijacking
  • ID: T1563.001
  • Reference URL: https://attack.mitre.org/techniques/T1563/001/

• Technique:

  • Name: Remote Services
  • ID: T1021
  • Reference URL: https://attack.mitre.org/techniques/T1021/

• Sub-technique:

  • Name: SSH
  • ID: T1021.004
  • Reference URL: https://attack.mitre.org/techniques/T1021/004/