Tampering of Bash Command-Line History

Adversaries may attempt to clear or disable the Bash command-line history in an attempt to evade detection or forensic investigations.

Rule type: eql

Rule indices:

auditbeat-*
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: None

Tags:

Elastic
Host
Linux
macOS
Threat Detection
Defense Evasion

Version: 8

Rule authors:

Elastic

Rule license: Elastic License v2

Investigation guide

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## Config

If enabling an EQL rule on a non-elastic-agent index (such as beats) for versions <8.2, events will not define `event.ingested` and default fallback for EQL rules was not added until 8.2, so you will need to add a custom pipeline to populate `event.ingested` to @timestamp for this rule to work.

Rule query

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process where event.type in ("start", "process_started") and
 (
  ((process.args : ("rm", "echo") or
    (process.args : "ln" and process.args : "-sf" and process.args : "/dev/null") or
    (process.args : "truncate" and process.args : "-s0"))
    and process.args : (".bash_history", "/root/.bash_history", "/home/*/.bash_history","/Users/.bash_history", "/Users/*/.bash_history",
                        ".zsh_history", "/root/.zsh_history", "/home/*/.zsh_history", "/Users/.zsh_history", "/Users/*/.zsh_history")) or
  (process.name : "history" and process.args : "-c") or
  (process.args : "export" and process.args : ("HISTFILE=/dev/null", "HISTFILESIZE=0")) or
  (process.args : "unset" and process.args : "HISTFILE") or
  (process.args : "set" and process.args : "history" and process.args : "+o")
 )

Framework: MITRE ATT&CK^TM

Tactic:
- Name: Defense Evasion
- ID: TA0005
- Reference URL: https://attack.mitre.org/tactics/TA0005/
Technique:
- Name: Indicator Removal on Host
- ID: T1070
- Reference URL: https://attack.mitre.org/techniques/T1070/
Sub-technique:
- Name: Clear Command History
- ID: T1070.003
- Reference URL: https://attack.mitre.org/techniques/T1070/003/

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