ID | Technique | Tactic |
---|---|---|
T1112 | Modify Registry | Defense Evasion |
Detection: Windows Defender ASR Rule Disabled
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.
Search
1`ms_defender` EventCode IN (5007)
2| rex field=New_Value "0x(?<New_Registry_Value>\\d+)$"
3| rex field=Old_Value "0x(?<Old_Registry_Value>\\d+)$"
4| rex field=New_Value "Rules\\\\(?<ASR_ID>[A-Fa-f0-9\\-]+)\\s*="
5| 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")
6| 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")
7| search New_Registry_Value="Disabled"
8| stats count min(_time) as firstTime max(_time) as lastTime by host, New_Value, Old_Value, Old_Registry_Value, New_Registry_Value, ASR_ID
9| lookup asr_rules ID AS ASR_ID OUTPUT ASR_Rule
10| `security_content_ctime(firstTime)`
11| `security_content_ctime(lastTime)`
12| rename host as dest
13| `windows_defender_asr_rule_disabled_filter`
Data Source
Name | Platform | Sourcetype | Source | Supported App |
---|---|---|---|---|
Windows Event Log Defender 5007 | Windows | 'xmlwineventlog' |
'WinEventLog:Microsoft-Windows-Windows Defender/Operational' |
N/A |
Macros Used
Name | Value |
---|---|
ms_defender | source="WinEventLog:Microsoft-Windows-Windows Defender/Operational" |
windows_defender_asr_rule_disabled_filter | search * |
windows_defender_asr_rule_disabled_filter
is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.
Annotations
Default Configuration
This detection is configured by default in Splunk Enterprise Security to run with the following settings:
Setting | Value |
---|---|
Disabled | true |
Cron Schedule | 0 * * * * |
Earliest Time | -70m@m |
Latest Time | -10m@m |
Schedule Window | auto |
Creates Notable | Yes |
Rule Title | %name% |
Rule Description | %description% |
Notable Event Fields | user, dest |
Creates Risk Event | True |
Implementation
The following analytic requires collection of Windows Defender Operational logs in either XML or multi-line. To collect, setup a new input for the Windows Defender Operational logs. In addition, it does require a lookup that maps the ID to ASR Rule name.
Known False Positives
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.
Associated Analytic Story
Risk Based Analytics (RBA)
Risk Message | Risk Score | Impact | Confidence |
---|---|---|---|
ASR rule disabled event, $ASR_Rule$, was triggered on $dest$. | 100 | 100 | 100 |
References
Detection Testing
Test Type | Status | Dataset | Source | Sourcetype |
---|---|---|---|---|
Validation | ✅ Passing | N/A | N/A | N/A |
Unit | ✅ Passing | Dataset | WinEventLog:Microsoft-Windows-Windows Defender/Operational |
xmlwineventlog |
Integration | ✅ Passing | Dataset | WinEventLog:Microsoft-Windows-Windows Defender/Operational |
xmlwineventlog |
Replay any dataset to Splunk Enterprise by using our replay.py
tool or the UI.
Alternatively you can replay a dataset into a Splunk Attack Range
Source: GitHub | Version: 3