Detection rules › Splunk
Spoolsv Suspicious Loaded Modules
The following analytic detects the suspicious loading of DLLs by spoolsv.exe, potentially indicating PrintNightmare exploitation. It leverages Sysmon EventCode 7 to identify instances where spoolsv.exe loads multiple DLLs from the Windows System32 spool drivers x64 directory. This activity is significant as it may signify an attacker exploiting the PrintNightmare vulnerability to execute arbitrary code. If confirmed malicious, this could lead to unauthorized code execution, privilege escalation, and persistent access within the environment, posing a severe security risk.
MITRE ATT&CK coverage
| Tactic | Techniques |
|---|---|
| Persistence | T1547.012 Boot or Logon Autostart Execution: Print Processors |
| Privilege Escalation | T1547.012 Boot or Logon Autostart Execution: Print Processors |
Event coverage
| Provider | Event ID | Title |
|---|---|---|
| Sysmon | 7 | Image loaded |
Stages and Predicates
Stage 1: search
search EventCode=7 Image="*\\spoolsv.exe" ImageLoaded="*.dll" ImageLoaded="*\\Windows\\System32\\spool\\drivers\\x64\\*"
Stage 2: stats
stats dc(ImageLoaded) AS countImgloaded, … AS ImageLoaded, … AS loaded_file, … AS loaded_file_path, … AS original_file_name, … AS process_exec, … AS process_guid, … AS process_hash, … AS process_name, … AS service_dll_signature_exists, … AS service_dll_signature_verified, … AS signature, … AS signature_id, … AS user_id, … AS vendor_product, … AS Image BY process_path, dest, process_id
Stage 3: where
where countImgloaded>=3
Stage 4: search
search
Stage 5: search
search
Stage 6: search
search `macro`
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 | eq |
|
ImageLoaded | eq |
|
countImgloaded | ge |
|
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 3 filters this rule applies)