Try in Splunk Security Cloud

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.

  • Type: Hunting

  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud

  • Last Updated: 2024-05-21
  • Author: Michael Haag, Splunk
  • ID: 425a6657-c5e4-4cbb-909e-fc9e5d326f01

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1566.001 Spearphishing Attachment Initial Access
T1566.002 Spearphishing Link Initial Access
T1059 Command and Scripting Interpreter Execution
Kill Chain Phase
  • Delivery
  • Installation
NIST
  • DE.AE
CIS20
  • CIS 10
CVE 


1
2
3
4
5
6
7
8



`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`

Macros

The SPL above uses the following Macros:

:information_source: windows_defender_asr_rules_stacking_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Lookups

The SPL above uses the following Lookups:

Required fields

List of fields required to use this analytic.

  • host
  • Parent_Commandline
  • Target_Commandline
  • ID
  • EventCode
  • ASR_Rule

How To Implement

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. The analytic can be modified to look for specific ASR rules, or to look for specific Event IDs. EventID 5007 is a change in the registry, and may be a false positive. This can be removed from the search if desired.

Known False Positives

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.

Associated Analytic Story

RBA

Risk Score Impact Confidence Message
50.0 50 100 An ASR rule, $ASR_Rule$, was triggered on $dest$.

:information_source: The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

Reference

Test Dataset

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 | version: 2