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Potential OpenSSH Backdoor Logging Activity

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Potential OpenSSH Backdoor Logging Activity

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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.*

Severity: high

Risk score: 73

Runs every: 5 minutes

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

Maximum alerts per execution: 100

References:

Tags:

Elastic
Host
Linux
Threat Detection
Persistence
Credential Access

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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Updates to approved and trusted SSH executables can trigger this rule.

Investigation guide

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Rule query

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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" ) )

Threat mapping

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Framework: MITRE ATT&CK^TM

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/
Tactic:
- Name: Persistence
- ID: TA0003
- Reference URL: https://attack.mitre.org/tactics/TA0003/
Technique:
- Name: Compromise Client Software Binary
- ID: T1554
- Reference URL: https://attack.mitre.org/techniques/T1554/

Rule version history

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Version 100 (8.5.0 release)

Formatting only

Version 4 (8.4.0 release)

Updated query, changed from:

file where event.type == "change" and process.executable :
("/usr/sbin/sshd", "/usr/bin/ssh") and ( file.name : (".*",
"~*") 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" ) )

Version 2 (8.2.0 release)

Formatting only

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