Suspicious Event Log Service Behavior

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Description

The following analytic utilizes Windows Event ID 1100 to identify when Windows event log service is shutdown. Note that this is a voluminous analytic that will require tuning or restricted to specific endpoints based on criticality. This event generates every time Windows Event Log service has shut down. It also generates during normal system shutdown. During triage, based on time of day and user, determine if this was planned. If not planned, follow through with reviewing parallel alerts and other data sources to determine what else may have occurred.

• Type: TTP

• Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud

• Last Updated: 2021-06-17
• Author: Mauricio Velazco, Splunk
• ID: 2b85aa3d-f5f6-4c2e-a081-a09f6e1c2e40

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

(`wineventlog_security` EventCode=1100) 
| stats count min(_time) as firstTime max(_time) as lastTime by dest Message EventCode 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| `suspicious_event_log_service_behavior_filter`

Macros

The SPL above uses the following Macros:

• wineventlog_security
• security_content_ctime

suspicious_event_log_service_behavior_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
• EventCode
• dest

How To Implement

To successfully implement this search, you need to be ingesting Windows event logs from your hosts. In addition, the Splunk Windows TA is needed.

Known False Positives

It is possible the Event Logging service gets shut down due to system errors or legitimately administration tasks. Filter as needed.

Associated Analytic Story

• Windows Log Manipulation
• Ransomware
• Clop Ransomware

RBA

Risk Score	Impact	Confidence	Message
9.0	30	30	The Windows Event Log Service shutdown on $ComputerName$

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://docs.microsoft.com/en-us/windows/security/threat-protection/auditing/event-1100
• https://www.ired.team/offensive-security/defense-evasion/disabling-windows-event-logs-by-suspending-eventlog-service-threads
• https://attack.mitre.org/techniques/T1070/001/
• https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1070.001/T1070.001.md

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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