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Linux Restricted Shell Breakout via c89/c99 Shell evasion
editLinux Restricted Shell Breakout via c89/c99 Shell evasion
editIdentifies Linux binary c89/c99 abuse to break out from restricted environments by spawning an interactive system shell.The c89/c99 utility is an interface to the standard C compilation system and the activity of spawing a shell is not a standard use of this binary by a user or system administrator. It indicates a potentially 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: 5m
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
Rule authors:
- Elastic
Rule license: Elastic License v2
Rule query
editprocess where event.type == "start" and process.name in ("sh", "dash", "bash") and
process.parent.name in ("c89","c99") and process.parent.args == "-wrapper" and
process.parent.args in ("sh,-s", "bash,-s", "dash,-s", "/bin/sh,-s", "/bin/bash,-s", "/bin/dash,-s")
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/
-
Sub-technique:
- Name: Unix Shell
- ID: T1059.004
- Reference URL: https://attack.mitre.org/techniques/T1059/004/