Detection rules › Sigma
Fax Service DLL Search Order Hijack
The Fax service attempts to load ualapi.dll, which is non-existent. An attacker can then (side)load their own malicious DLL using this service.
MITRE ATT&CK coverage
| Tactic | Techniques |
|---|---|
| Persistence | T1574.001 Hijack Execution Flow: DLL |
| Privilege Escalation | T1574.001 Hijack Execution Flow: DLL |
| Defense Evasion | T1574.001 Hijack Execution Flow: DLL |
Event coverage
| Provider | Event ID | Title |
|---|---|---|
| Sysmon | 7 | Image loaded |
Stages and Predicates
Stage 1: selection
Image|endswith: '\fxssvc.exe'
ImageLoaded|endswith: ualapi.dll
Stage 2: not filter
ImageLoaded|startswith: 'C:\Windows\WinSxS\'
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 |
|---|---|---|
Image | ends_with |
|
ImageLoaded | ends_with |
|
ImageLoaded | starts_with |
|