ID | Technique | Tactic |
---|---|---|
T1485 | Data Destruction | Impact |
Detection: Excessive File Deletion In WinDefender Folder
Description
The following analytic detects excessive file deletion events in the Windows Defender folder. It leverages Sysmon EventCodes 23 and 26 to identify processes deleting multiple files within this directory. This behavior is significant as it may indicate an attempt to corrupt or disable Windows Defender, a key security component. If confirmed malicious, this activity could allow an attacker to disable endpoint protection, facilitating further malicious actions without detection.
Search
1`sysmon` EventCode IN ("23","26") TargetFilename = "*\\ProgramData\\Microsoft\\Windows Defender\\*"
2| stats count, values(TargetFilename) as deleted_files, min(_time) as firstTime, max(_time) as lastTime by user, dest, signature, signature_id, Image, process_name, process_guid
3| rename Image as process
4| where count >=50
5| `security_content_ctime(firstTime)`
6| `security_content_ctime(lastTime)`
7| `excessive_file_deletion_in_windefender_folder_filter`
Data Source
Name | Platform | Sourcetype | Source | Supported App |
---|---|---|---|---|
Sysmon EventID 23 | Windows | 'xmlwineventlog' |
'XmlWinEventLog:Microsoft-Windows-Sysmon/Operational' |
N/A |
Macros Used
Name | Value |
---|---|
security_content_ctime | convert timeformat="%Y-%m-%dT%H:%M:%S" ctime($field$) |
excessive_file_deletion_in_windefender_folder_filter | search * |
excessive_file_deletion_in_windefender_folder_filter
is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.
Annotations
Default Configuration
This detection is configured by default in Splunk Enterprise Security to run with the following settings:
Setting | Value |
---|---|
Disabled | true |
Cron Schedule | 0 * * * * |
Earliest Time | -70m@m |
Latest Time | -10m@m |
Schedule Window | auto |
Creates Notable | Yes |
Rule Title | %name% |
Rule Description | %description% |
Notable Event Fields | user, dest |
Creates Risk Event | True |
Implementation
To successfully implement this search, you must ingest logs that include the process name, TargetFilename, and ProcessID executions from your endpoints. If you are utilizing Sysmon, ensure you have at least version 2.0 of the Sysmon TA installed.
Known False Positives
Windows Defender AV updates may trigger this alert. Please adjust the filter macros to mitigate false positives.
Associated Analytic Story
Risk Based Analytics (RBA)
Risk Message | Risk Score | Impact | Confidence |
---|---|---|---|
Excessive file deletion events were detected in the Windows Defender folder on $dest$ by $user$. Investigate further to determine if this activity is malicious. | 25 | 50 | 50 |
References
Detection Testing
Test Type | Status | Dataset | Source | Sourcetype |
---|---|---|---|---|
Validation | ✅ Passing | N/A | N/A | N/A |
Unit | ✅ Passing | Dataset | XmlWinEventLog:Microsoft-Windows-Sysmon/Operational |
xmlwineventlog |
Integration | ✅ Passing | Dataset | XmlWinEventLog:Microsoft-Windows-Sysmon/Operational |
xmlwineventlog |
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
Source: GitHub | Version: 3