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SSH Authorized Keys File Modification

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SSH Authorized Keys File Modification

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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: 5 minutes

Searches indices from: now-9m (Date Math format, see also Additional look-back time)

Maximum alerts per execution: 100

Tags:

Elastic
Host
Linux
macOS
Threat Detection
Persistence

Version: 100 (version history)

Added (Elastic Stack release): 7.12.0

Last modified (Elastic Stack release): 8.5.0

Rule authors: Elastic

Rule license: Elastic License v2

Rule query

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event.category:file and event.type:(change or creation) and
file.name:("authorized_keys" or "authorized_keys2") 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)

Threat mapping

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Framework: MITRE ATT&CK^TM

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/

Rule version history

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Version 100 (8.5.0 release)

Updated query, changed from:

event.category:file and event.type:(change or creation) and
file.name:("authorized_keys" or "authorized_keys2") 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)

Version 3 (8.4.0 release)

Formatting only

Version 2 (8.3.0 release)

Updated query, changed from:

event.category:file and event.type:(change or creation) and
file.name:("authorized_keys" or "authorized_keys2") 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/*)

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