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Potential OpenSSH Backdoor Logging Activity

Elastic Stack Serverless Security

Identifies a Secure Shell (SSH) client or server process creating or writing to a known SSH backdoor log file. Adversaries may modify SSH related binaries for persistence or credential access via patching sensitive functions to enable unauthorized access or to log SSH credentials for exfiltration.

Rule type: eql

Rule indices:

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

Severity: high

Risk score: 73

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:

Tags:

  • Elastic
  • Host
  • Linux
  • Threat Detection
  • Persistence
  • Credential Access
  • Elastic Endgame

Version: 102

Rule authors:

  • Elastic

Rule license: Elastic License v2

Investigation guide

Rule query

file where event.type == "change" and process.executable : ("/usr/sbin/sshd", "/usr/bin/ssh") and
  (
    (file.name : (".*", "~*", "*~") and not file.name : (".cache", ".viminfo", ".bash_history")) or
    file.extension : ("in", "out", "ini", "h", "gz", "so", "sock", "sync", "0", "1", "2", "3", "4", "5", "6", "7", "8", "9") or
    file.path :
    (
      "/private/etc/*--",
      "/usr/share/*",
      "/usr/include/*",
      "/usr/local/include/*",
      "/private/tmp/*",
      "/private/var/tmp/*",
      "/usr/tmp/*",
      "/usr/share/man/*",
      "/usr/local/share/*",
      "/usr/lib/*.so.*",
      "/private/etc/ssh/.sshd_auth",
      "/usr/bin/ssd",
      "/private/var/opt/power",
      "/private/etc/ssh/ssh_known_hosts",
      "/private/var/html/lol",
      "/private/var/log/utmp",
      "/private/var/lib",
      "/var/run/sshd/sshd.pid",
      "/var/run/nscd/ns.pid",
      "/var/run/udev/ud.pid",
      "/var/run/udevd.pid"
    )
  )

Framework: MITRE ATT&CKTM