SSH Authorized Keys File Modification

  1[metadata]
  2creation_date = "2020/12/22"
  3integration = ["endpoint"]
  4maturity = "production"
  5min_stack_comments = "Multiple field support in the New Terms rule type was added in Elastic 8.6"
  6min_stack_version = "8.6.0"
  7updated_date = "2024/02/22"
  8
  9[rule]
 10author = ["Elastic"]
 11description = """
 12The Secure Shell (SSH) authorized_keys file specifies which users are allowed to log into a server using public key
 13authentication. Adversaries may modify it to maintain persistence on a victim host by adding their own public key(s).
 14"""
 15from = "now-9m"
 16index = ["auditbeat-*", "logs-endpoint.events.*"]
 17language = "kuery"
 18license = "Elastic License v2"
 19name = "SSH Authorized Keys File Modification"
 20risk_score = 47
 21rule_id = "2215b8bd-1759-4ffa-8ab8-55c8e6b32e7f"
 22severity = "medium"
 23tags = ["Domain: Endpoint",
 24        "OS: Linux",
 25        "OS: macOS",
 26        "Use Case: Threat Detection",
 27        "Tactic: Lateral Movement",
 28        "Tactic: Persistence",
 29        "Data Source: Elastic Defend"
 30        ]
 31timestamp_override = "event.ingested"
 32type = "new_terms"
 33query = '''
 34event.category:file and event.type:(change or creation) and
 35 file.name:("authorized_keys" or "authorized_keys2" or "/etc/ssh/sshd_config" or "/root/.ssh") and
 36 not process.executable:
 37             (/Library/Developer/CommandLineTools/usr/bin/git or
 38              /usr/local/Cellar/maven/*/libexec/bin/mvn or
 39              /Library/Java/JavaVirtualMachines/jdk*.jdk/Contents/Home/bin/java or
 40              /usr/bin/vim or
 41              /usr/local/Cellar/coreutils/*/bin/gcat or
 42              /usr/bin/bsdtar or
 43              /usr/bin/nautilus or
 44              /usr/bin/scp or
 45              /usr/bin/touch or
 46              /var/lib/docker/* or
 47              /usr/bin/google_guest_agent or 
 48              /opt/jc/bin/jumpcloud-agent or 
 49              /opt/puppetlabs/puppet/bin/puppet or
 50              /usr/bin/chef-client
 51)
 52'''
 53
 54[[rule.threat]]
 55framework = "MITRE ATT&CK"
 56
 57[[rule.threat.technique]]
 58id = "T1098"
 59name = "Account Manipulation"
 60reference = "https://attack.mitre.org/techniques/T1098/"
 61
 62[[rule.threat.technique.subtechnique]]
 63id = "T1098.004"
 64name = "SSH Authorized Keys"
 65reference = "https://attack.mitre.org/techniques/T1098/004/"
 66
 67[rule.threat.tactic]
 68id = "TA0003"
 69name = "Persistence"
 70reference = "https://attack.mitre.org/tactics/TA0003/"
 71
 72[[rule.threat]]
 73framework = "MITRE ATT&CK"
 74
 75[[rule.threat.technique]]
 76id = "T1563"
 77name = "Remote Service Session Hijacking"
 78reference = "https://attack.mitre.org/techniques/T1563/"
 79
 80[[rule.threat.technique.subtechnique]]
 81id = "T1563.001"
 82name = "SSH Hijacking"
 83reference = "https://attack.mitre.org/techniques/T1563/001/"
 84
 85[[rule.threat.technique]]
 86id = "T1021"
 87name = "Remote Services"
 88reference = "https://attack.mitre.org/techniques/T1021/"
 89
 90[[rule.threat.technique.subtechnique]]
 91id = "T1021.004"
 92name = "SSH"
 93reference = "https://attack.mitre.org/techniques/T1021/004/"
 94
 95[rule.threat.tactic]
 96id = "TA0008"
 97name = "Lateral Movement"
 98reference = "https://attack.mitre.org/tactics/TA0008/"
 99
100[rule.new_terms]
101field = "new_terms_fields"
102value = ["host.id", "process.executable"]
103
104[[rule.new_terms.history_window_start]]
105field = "history_window_start"
106value = "now-10d"