Detection: Modification Of Wallpaper

Description

The following analytic detects the modification of registry keys related to the desktop wallpaper settings. It leverages Sysmon EventCode 13 to identify changes to the "Control Panel\Desktop\Wallpaper" and "Control Panel\Desktop\WallpaperStyle" registry keys, especially when the modifying process is not explorer.exe or involves suspicious file paths like temp or public directories. This activity is significant as it can indicate ransomware behavior, such as the REVIL ransomware, which changes the wallpaper to display a ransom note. If confirmed malicious, this could signify a compromised machine and the presence of ransomware, leading to potential data encryption and extortion.

Search

1`sysmon` EventCode =13  (TargetObject IN ("*\\Control Panel\\Desktop\\Wallpaper","*\\Control Panel\\Desktop\\WallpaperStyle") AND Image != "*\\explorer.exe") OR (TargetObject IN ("*\\Control Panel\\Desktop\\Wallpaper","*\\Control Panel\\Desktop\\WallpaperStyle") AND Details IN ("*\\temp\\*", "*\\users\\public\\*")) 
2| stats count min(_time) as firstTime max(_time) as lastTime by action dest process_guid process_id registry_hive registry_path registry_key_name registry_value_data registry_value_name status user_id vendor_product 
3| `security_content_ctime(firstTime)` 
4| `security_content_ctime(lastTime)` 
5| `modification_of_wallpaper_filter`

Data Source

Name	Platform	Sourcetype	Source
Sysmon EventID 13	Windows	'XmlWinEventLog'	'XmlWinEventLog:Microsoft-Windows-Sysmon/Operational'

Macros Used

Annotations

Default Configuration

This detection is configured by default in Splunk Enterprise Security to run with the following settings:

Implementation

To successfully implement this search, you need to be ingesting logs with the Image, TargetObject registry key, registry Details from your endpoints. If you are using Sysmon, you must have at least version 6.0.4 of the Sysmon TA.

Known False Positives

3rd party tool may used to changed the wallpaper of the machine

Associated Analytic Story

• Rhysida Ransomware

• Ransomware

• Brute Ratel C4

• ZOVWiper

• Windows Registry Abuse

• LockBit Ransomware

• BlackMatter Ransomware

• Revil Ransomware

• Black Basta Ransomware

Finding

References

• https://news.sophos.com/en-us/2020/04/24/lockbit-ransomware-borrows-tricks-to-keep-up-with-revil-and-maze/

• https://www.mcafee.com/blogs/other-blogs/mcafee-labs/mcafee-atr-analyzes-sodinokibi-aka-revil-ransomware-as-a-service-what-the-code-tells-us/

• https://krebsonsecurity.com/2021/05/a-closer-look-at-the-darkside-ransomware-gang/

Detection Testing

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: 11