Techniques
Sample rules
Windows Defacement Modify Transcodedwallpaper File
- source: splunk
- technicques:
- T1491
Description
The following analytic identifies modifications to the TranscodedWallpaper file in the wallpaper theme directory, excluding changes made by explorer.exe. This detection leverages the Endpoint.Processes and Endpoint.Filesystem data models to correlate process activity with file modifications. This activity is significant as it may indicate an adversary attempting to deface or change the desktop wallpaper of a targeted host, a tactic often used to signal compromise or deliver a message. If confirmed malicious, this could be a sign of unauthorized access and tampering, potentially leading to further system compromise or data exfiltration.
Detection logic
| tstats `security_content_summariesonly` count FROM datamodel=Endpoint.Processes where Processes.process_path !="*\\Windows\\Explorer.EXE" by _time span=1h Processes.process_id Processes.process_name Processes.process Processes.dest Processes.process_guid Processes.original_file_name
| `drop_dm_object_name(Processes)`
|rename process_guid as proc_guid
| join proc_guid, _time [
| tstats `security_content_summariesonly` count FROM datamodel=Endpoint.Filesystem where Filesystem.file_path = "*\\AppData\\Roaming\\Microsoft\\Windows\\Themes\\TranscodedWallpaper" by _time span=1h Filesystem.dest Filesystem.file_create_time Filesystem.file_name Filesystem.file_path Filesystem.process_guid
| `drop_dm_object_name(Filesystem)`
|rename process_guid as proc_guid
| fields file_name file_path process_name process_path process dest file_create_time _time proc_guid]
| `windows_defacement_modify_transcodedwallpaper_file_filter`