Sigma rule: BaaUpdate.exe Suspicious DLL Load

Rule

Title

BaaUpdate.exe Suspicious DLL Load

Status

experimental

Level

high

Author

Swachchhanda Shrawan Poudel (Nextron Systems)

Date

2025-10-18

File

rules/windows/image_load/image_load_susp_baaupdate_dll_load.yml

Commit

ccbb0369507f796db0b0ae6854c8a2be471b9d84

Detects BitLocker Access Agent Update Utility (baaupdate.exe) loading DLLs from suspicious locations that are publicly writable which could indicate an attempt to lateral movement via BitLocker DCOM & COM Hijacking.
This technique abuses COM Classes configured as INTERACTIVE USER to spawn processes in the context of the logged-on user's session. Specifically, it targets the BDEUILauncher Class (CLSID ab93b6f1-be76-4185-a488-a9001b105b94)
which can launch BaaUpdate.exe, which is vulnerable to COM Hijacking when started with input parameters. This allows attackers to execute code in the user's context without needing to steal credentials or use additional techniques to compromise the account.

Log source

product

windows

category

image_load

Detection

selection:
    Image|endswith: '\BaaUpdate.exe'
    ImageLoaded|endswith: '.dll'
    ImageLoaded|contains:
        - ':\Perflogs\'
        - ':\Users\Default\'
        - ':\Users\Public\'
        - ':\Windows\Temp\'
        - '\AppData\Local\Temp\'
        - '\AppData\Roaming\'
        - '\Contacts\'
        - '\Favorites\'
        - '\Favourites\'
        - '\Links\'
        - '\Music\'
        - '\Pictures\'
        - '\ProgramData\'
        - '\Temporary Internet'
        - '\Videos\'
condition: selection

False positives (as the rule lists them)

• Unknown

Tags

• attack.stealth
• attack.t1218
• attack.lateral-movement
• attack.t1021.003

MITRE ATT&CK ids this rule names

• T1021.003
• T1218

Related rules

• 9f38c1db-e2ae-40bf-81d0-5b68f73fb512 (similar)

References

• https://github.com/rtecCyberSec/BitlockMove

Read on 2026-11-03T00:58:21.399Z under licence sigma-drl-1.1@d5f4c36a from https://github.com/SigmaHQ/sigma/blob/ccbb0369507f796db0b0ae6854c8a2be471b9d84/rules/windows/image_load/image_load_susp_baaupdate_dll_load.yml