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Modification of OpenSSH Binaries

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Modification of OpenSSH Binaries

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Adversaries may modify SSH related binaries for persistence or credential access by patching sensitive functions to enable unauthorized access or by logging SSH credentials for exfiltration.

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

References:

https://blog.angelalonso.es/2016/09/anatomy-of-real-linux-intrusion-part-ii.html

Tags:

Elastic
Host
Linux
Threat Detection
Credential Access
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

Potential false positives

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Trusted OpenSSH executable updates. It’s recommended to verify the integrity of OpenSSH binary changes.

Rule query

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event.category:file and event.type:change and process.name:* and
(file.path:(/usr/sbin/sshd or /usr/bin/ssh or /usr/bin/sftp or
/usr/bin/scp) or file.name:libkeyutils.so) and not
process.name:("dpkg" or "yum" or "dnf" or "dnf-automatic")

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: Create or Modify System Process
- ID: T1543
- Reference URL: https://attack.mitre.org/techniques/T1543/
Tactic:
- Name: Credential Access
- ID: TA0006
- Reference URL: https://attack.mitre.org/tactics/TA0006/
Technique:
- Name: Modify Authentication Process
- ID: T1556
- Reference URL: https://attack.mitre.org/techniques/T1556/

Rule version history

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Version 100 (8.5.0 release)

Formatting only

Version 3 (8.4.0 release)

Updated query, changed from:

event.category:file and event.type:change and process.name:* and
(file.path:(/usr/sbin/sshd or /usr/bin/ssh or /usr/bin/sftp or
/usr/bin/scp) or file.name:libkeyutils.so) and not
process.executable:/usr/bin/dpkg

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