ID | Technique | Tactic |
---|---|---|
T1059 | Command and Scripting Interpreter | Execution |
T1566.001 | Spearphishing Attachment | Initial Access |
T1566.002 | Spearphishing Link | Initial Access |
Detection: Windows Defender ASR Block Events
Description
This detection searches for Windows Defender ASR block 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 block events that are generated when a process or application attempts to perform an action that is blocked by an ASR rule. Typically, these will be enabled in block most after auditing and tuning the ASR rules themselves. Set to TTP once tuned.
Search
1`ms_defender` EventCode IN (1121, 1126, 1129, 1131, 1133)
2| stats count min(_time) as firstTime max(_time) as lastTime by host, Path, Parent_Commandline, Process_Name, ID, EventCode
3| lookup asr_rules ID OUTPUT ASR_Rule
4| fillnull value=NULL
5| `security_content_ctime(firstTime)`
6| `security_content_ctime(lastTime)`
7| rename host as dest
8| `windows_defender_asr_block_events_filter`
Data Source
Name | Platform | Sourcetype | Source | Supported App |
---|---|---|---|---|
Windows Event Log Defender 1121 | 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_block_events_filter | search * |
windows_defender_asr_block_events_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 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. Note that Audit and block Event IDs have different fields, therefore the analytic will need to be modified for each type of event.
Known False Positives
False positives are expected from legitimate applications generating events that are similar to those generated by malicious activity. For example, Event ID 1122 is generated when a process attempts to load a DLL that is blocked by an ASR rule. This can be triggered by legitimate applications that attempt to load DLLs that are not blocked by ASR rules. This is block only.
Associated Analytic Story
Risk Based Analytics (RBA)
Risk Message | Risk Score | Impact | Confidence |
---|---|---|---|
ASR block event, $ASR_Rule$, was triggered on $dest$. | 45 | 50 | 90 |
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