IMPORTANT: No additional bug fixes or documentation updates will be released for this version. For the latest information, see the current release documentation.
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Clearing Windows Event Logs

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Clearing Windows Event Logs

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Identifies attempts to clear or disable Windows event log stores using Windows wevetutil command. This is often done by attackers in an attempt to evade detection or destroy forensic evidence on a system.

Rule type: eql

Rule indices:

  • winlogbeat-*
  • logs-endpoint.events.process-*
  • logs-windows.*
  • endgame-*
  • logs-system.security*

Severity: low

Risk score: 21

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:

  • Domain: Endpoint
  • OS: Windows
  • Use Case: Threat Detection
  • Tactic: Defense Evasion
  • Resources: Investigation Guide
  • Data Source: Elastic Endgame
  • Data Source: Elastic Defend

Version: 112

Rule authors:

  • Elastic

Rule license: Elastic License v2

Investigation guide

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Triage and analysis

Investigating Clearing Windows Event Logs

Windows event logs are a fundamental data source for security monitoring, forensics, and incident response. Adversaries can tamper, clear, and delete this data to break SIEM detections, cover their tracks, and slow down incident response.

This rule looks for the execution of the wevtutil.exe utility or the Clear-EventLog cmdlet to clear event logs.

Possible investigation steps

  • Investigate the process execution chain (parent process tree) for unknown processes. Examine their executable files for prevalence, whether they are located in expected locations, and if they are signed with valid digital signatures.
  • Identify the user account that performed the action and whether it should perform this kind of action.
  • Contact the account owner and confirm whether they are aware of this activity.
  • Investigate other alerts associated with the user/host during the past 48 hours.
  • Verify if any other anti-forensics behaviors were observed.
  • Investigate the event logs prior to the action for suspicious behaviors that an attacker may be trying to cover up.

False positive analysis

  • This mechanism can be used legitimately. Analysts can dismiss the alert if the administrator is aware of the activity and there are justifications for this action.
  • Analyze whether the cleared event log is pertinent to security and general monitoring. Administrators can clear non-relevant event logs using this mechanism. If this activity is expected and noisy in your environment, consider adding exceptions — preferably with a combination of user and command line conditions.

Response and remediation

  • Initiate the incident response process based on the outcome of the triage.
  • This activity is potentially done after the adversary achieves its objectives on the host. Ensure that previous actions, if any, are investigated accordingly with their response playbooks.
  • Isolate the involved host to prevent further post-compromise behavior.
  • Investigate credential exposure on systems compromised or used by the attacker to ensure all compromised accounts are identified. Reset passwords for these accounts and other potentially compromised credentials, such as email, business systems, and web services.
  • Run a full antimalware scan. This may reveal additional artifacts left in the system, persistence mechanisms, and malware components.
  • Determine the initial vector abused by the attacker and take action to prevent reinfection through the same vector.
  • Using the incident response data, update logging and audit policies to improve the mean time to detect (MTTD) and the mean time to respond (MTTR).

Setup

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Setup

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 version 8.2. Hence for this rule to work effectively, users will need to add a custom ingest pipeline to populate event.ingested to @timestamp. For more details on adding a custom ingest pipeline refer - https://www.elastic.co/guide/en/fleet/current/data-streams-pipeline-tutorial.html

Rule query

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process where host.os.type == "windows" and event.type == "start" and
(
  (
    (process.name : "wevtutil.exe" or ?process.pe.original_file_name == "wevtutil.exe") and
    process.args : ("/e:false", "cl", "clear-log")
  ) or
  (
    process.name : ("powershell.exe", "pwsh.exe", "powershell_ise.exe") and
    process.args : "Clear-EventLog"
  )
)

Framework: MITRE ATT&CKTM

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