LoFP LoFP / false positives are not expected with this analytic, since it is a hunting analytic. it is meant to show the use of asr rules and how they can be used to detect malicious activity.

Techniques

Sample rules

Windows Defender ASR Rules Stacking

Description

The following analytic identifies security events from Microsoft Defender, focusing on Exploit Guard and Attack Surface Reduction (ASR) features. It detects Event IDs 1121, 1126, 1131, and 1133 for blocked operations, and Event IDs 1122, 1125, 1132, and 1134 for audit logs. Event ID 1129 indicates user overrides, while Event ID 5007 signals configuration changes. This detection uses a lookup to correlate ASR rule GUIDs with descriptive names. Monitoring these events is crucial for identifying unauthorized operations, potential security breaches, and policy enforcement issues. If confirmed malicious, attackers could bypass security measures, execute unauthorized actions, or alter system configurations.

Detection logic

`ms_defender` EventCode IN (1121, 1122, 1125, 1126, 1129, 1131, 1132, 1133, 1134, 5007) 
| stats count min(_time) as firstTime max(_time) as lastTime by host Parent_Commandline, Process_Name, Path, ID, EventCode 
| lookup asr_rules ID OUTPUT ASR_Rule 
| fillnull value=NULL 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)`
| rename host as dest 
| `windows_defender_asr_rules_stacking_filter`