Disable Logs Using WevtUtil

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Description

This search is to detect execution of wevtutil.exe to disable logs. This technique was seen in several ransomware to disable the event logs to evade alerts and detections.

• Type: TTP
• Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
• Datamodel: Endpoint
• Last Updated: 2021-06-10
• Author: Teoderick Contreras, Splunk
• ID: 236e7c8e-c9d9-11eb-a824-acde48001122

Annotations

ATT&CK

ATT&CK

ID	Technique	Tactic
T1070	Indicator Removal	Defense Evasion

T1070.001

Clear Windows Event Logs

Defense Evasion

Kill Chain Phase

• Exploitation

NIST

• DE.CM

CIS20

• CIS 10

CVE

Search

| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime from datamodel=Endpoint.Processes where Processes.process_name = "wevtutil.exe" Processes.process = "*sl*" Processes.process = "*/e:false*" by Processes.parent_process_name Processes.parent_process Processes.process_name Processes.process Processes.dest Processes.user Processes.process_id Processes.process_guid 
| `drop_dm_object_name(Processes)` 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| `disable_logs_using_wevtutil_filter`

Macros

The SPL above uses the following Macros:

• security_content_ctime
• security_content_summariesonly

disable_logs_using_wevtutil_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Required fields

List of fields required to use this analytic.

• _time
• Processes.parent_process_name
• Processes.parent_process
• Processes.process_name
• Processes.process
• Processes.dest
• Processes.user
• Processes.process_id
• Processes.process_guid

How To Implement

To successfully implement this search, you need to be ingesting logs with the process name, parent process, and command-line executions from your endpoints. If you are using Sysmon, you must have at least version 6.0.4 of the Sysmon TA.

Known False Positives

network operator may disable audit event logs for debugging purposes.

Associated Analytic Story

• Ransomware

RBA

Risk Score	Impact	Confidence	Message
24.0	30	80	WevtUtil.exe used to disable Event Logging on $dest

The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

Reference

• https://www.bleepingcomputer.com/news/security/new-ransom-x-ransomware-used-in-texas-txdot-cyberattack/

Test Dataset

Replay any dataset to Splunk Enterprise by using our replay.py tool or the UI. Alternatively you can replay a dataset into a Splunk Attack Range

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