Detection rules › Splunk
CMLUA Or CMSTPLUA UAC Bypass
The following analytic detects the use of COM objects like CMLUA or CMSTPLUA to bypass User Account Control (UAC). It leverages Sysmon EventCode 7 to identify the loading of specific DLLs (CMLUA.dll, CMSTPLUA.dll, CMLUAUTIL.dll) by processes not typically associated with these libraries. This activity is significant as it indicates an attempt to gain elevated privileges, a common tactic used by ransomware adversaries. If confirmed malicious, this could allow attackers to execute code with administrative rights, leading to potential system compromise and further malicious activities.
MITRE ATT&CK coverage
| Tactic | Techniques |
|---|---|
| Defense Evasion | T1218.003 System Binary Proxy Execution: CMSTP |
Event coverage
| Provider | Event ID | Title |
|---|---|---|
| Sysmon | 7 | Image loaded |
Stages and Predicates
Stage 1: search
search NOT (NOT Image IN ("*\\program files*", "*\\windows\\*") process_name IN ("CMMGR32.exe", "CMSTP.exe")) EventCode=7 ImageLoaded IN ("*\\CMLUA.dll", "*\\CMLUAUTIL.dll", "*\\CMSTPLUA.dll")
Stage 2: fillnull
fillnull
Stage 3: stats
stats BY Image, ImageLoaded, dest, loaded_file, loaded_file_path, original_file_name, process_exec, process_guid, process_hash, process_id, process_name, process_path, service_dll_signature_exists, service_dll_signature_verified, signature, signature_id, user_id, vendor_product
Stage 4: search
search
Stage 5: search
search
Stage 6: search
search `macro`
Exclusions
Top-level NOT(...) conjuncts — predicates this rule actively suppresses.
| Stage | Field | Kind | Excluded values |
|---|---|---|---|
| 1 | Image | in | "*\\program files*", "*\\windows\\*" |
| 2 | process_name | in | "CMMGR32.exe", "CMSTP.exe" |
Indicators
Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.
| Field | Kind | Values |
|---|---|---|
EventCode | eq |
|
Image | in |
|
ImageLoaded | in |
|
Neighbors
Broader alternatives (more inclusive than this rule)
These rules match a superset of what this rule catches. They cover the same events plus more. Use them if you want wider coverage and can absorb more false positives.
- Windows Remote Access Software BRC4 Loaded Dll (drops 2 filters this rule applies)