Linux Restricted Shell Breakout via the expect commandedit
Identifies Linux binary expect command abuse to break out from restricted environments by spawning an interactive system shell. The expect utility allows us to automate control of interactive applications such as Telnet, FTP, SSH and others. The activity of spawning shell is not a standard use of this binary for a user or system administrator and could potentially indicate malicious actor attempting to improve the capabilities or stability of their access.
Rule type: eql
Rule indices:
- 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:
Tags:
- Elastic
- Host
- Linux
- Threat Detection
- Execution
- GTFOBins
Version: 1
Added (Elastic Stack release): 8.2.0
Rule authors: Elastic
Rule license: Elastic License v2
Rule queryedit
process where event.type == "start" and process.name in ("bash", "sh",
"dash") and process.parent.name == "expect" and process.parent.args
== "-c" and process.parent.args in ("spawn /bin/sh;interact", "spawn
/bin/bash;interact", "spawn /bin/dash;interact", "spawn sh;interact",
"spawn bash;interact", "spawn dash;interact")
Threat mappingedit
Framework: MITRE ATT&CKTM
-
Tactic:
- Name: Execution
- ID: TA0002
- Reference URL: https://attack.mitre.org/tactics/TA0002/
-
Technique:
- Name: Command and Scripting Interpreter
- ID: T1059
- Reference URL: https://attack.mitre.org/techniques/T1059/