false positives may occur if applications are typically disabling asr rules in the environment. monitor for changes to asr rules to determine if this is a false positive.

Techniques

T1112

Sample rules

Windows Defender ASR Rule Disabled

source: splunk
technicques:
- T1112

Description

The following analytic identifies when a Windows Defender ASR rule disabled events. ASR is a feature of Windows Defender Exploit Guard that prevents actions and apps that are typically used by exploit-seeking malware to infect machines. ASR rules are applied to processes and applications. When a process or application attempts to perform an action that is blocked by an ASR rule, an event is generated. This detection searches for ASR rule disabled events that are generated when an ASR rule is disabled.

Detection logic

`ms_defender` EventCode IN (5007) 
| rex field=New_Value "0x(?<New_Registry_Value>\\d+)$" 
| rex field=Old_Value "0x(?<Old_Registry_Value>\\d+)$" 
| rex field=New_Value "Rules\\\\(?<ASR_ID>[A-Fa-f0-9\\-]+)\\s*=" 
| lookup asr_rules ID AS ASR_ID OUTPUT ASR_Rule 
| eval New_Registry_Value=case(New_Registry_Value=="0", "Disabled", New_Registry_Value=="1", "Block", New_Registry_Value=="2", "Audit", New_Registry_Value=="6", "Warn") 
| eval Old_Registry_Value=case(Old_Registry_Value=="0", "Disabled", Old_Registry_Value=="1", "Block", Old_Registry_Value=="2", "Audit", Old_Registry_Value=="6", "Warn") 
| search New_Registry_Value="Disabled" 
| stats count min(_time) as firstTime max(_time) as lastTime by host, New_Value, Old_Value, Old_Registry_Value, New_Registry_Value, ASR_Rule 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)`
| rename host as dest 
| `windows_defender_asr_rule_disabled_filter`