Sigma rules to detect CVE 2025 29824 and susp BLF File Creation #5260
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Apr 15, 2025
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| selection_suspicious_paths_1: | ||
| TargetFilename|contains: | ||
| - ':\$Recycle.bin' | ||
| - ':\Perflogs' | ||
| - ':\ProgramData' | ||
| - ':\Temp' | ||
| - ':\Users\Default' | ||
| - ':\Users\public' | ||
| - ':\Windows\Temp' | ||
| - ':\Windows\addins' | ||
| - ':\Windows\Fonts' | ||
| - ':\Windows\IME' | ||
| - ':\Windows\System32\Tasks' | ||
| - ':\Windows\Tasks' | ||
| - '\config\systemprofile' | ||
| - '\AppData\Local\Temp' | ||
| - '\AppData\Roaming' | ||
| selection_suspicious_paths_user_1: | ||
| TargetFilename|contains: ':\Users\' | ||
| selection_suspicious_paths_user_2: | ||
| TargetFilename|contains: | ||
| - '\Contacts\' | ||
| - '\Documents\' | ||
| - '\Favorites\' | ||
| - '\Favourites\' | ||
| - '\Music\' | ||
| - '\Photos\' | ||
| - '\Pictures\' |
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.blf files should not be common so focusing on exclusion is far better than specifying a list that can be bypassed.
Also your list already contains FP such as C:\Users\Default\ and \config\systemprofile.
You cannot add a static list of potential susp paths without testing them first.
| selection_path: | ||
| TargetFilename|contains: ':\ProgramData\SkyPDF\' | ||
| selection_image: | ||
| Image|endswith: '\dllhost.exe' |
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Who is the process that usually writes .blf files? Are you sure its not dllhost?
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Summary of the Pull Request
Sigma rules to detect CVE 2025 29824 and susp BLF File Creation
Changelog
new: Potential Exploitation of CVE-2025-29824 - CLFS BLF File Creation (ET)
new: Suspicious BLF File Creation Outside System Directories
Example Log Event
Fixed Issues
SigmaHQ Rule Creation Conventions