Detection: Wermgr Process Create Executable File

Updated Date: 2024-05-23 ID: ab3bcce0-a105-11eb-973c-acde48001122 Author: Teoderick Contreras, Splunk Type: TTP Product: Splunk Enterprise Security

Description

The following analytic detects the wermgr.exe process creating an executable file. It leverages Sysmon EventCode 11 to identify instances where wermgr.exe generates a .exe file. This behavior is unusual because wermgr.exe is typically associated with error reporting, not file creation. Such activity is significant as it may indicate TrickBot malware, which injects code into wermgr.exe to execute malicious actions like downloading additional payloads. If confirmed malicious, this could lead to further malware infections, data exfiltration, or system compromise.

Search

1`sysmon` EventCode=11 process_name = "wermgr.exe" TargetFilename = "*.exe" 
2| stats  min(_time) as firstTime max(_time) as lastTime count by  Image TargetFilename process_name dest EventCode ProcessId 
3| `security_content_ctime(firstTime)` 
4| `security_content_ctime(lastTime)` 
5| `wermgr_process_create_executable_file_filter`

Data Source

Name	Platform	Sourcetype	Source	Supported App
Sysmon EventID 11	Windows	`'xmlwineventlog'`	`'XmlWinEventLog:Microsoft-Windows-Sysmon/Operational'`	N/A

Macros Used

Name	Value
security_content_ctime	`convert timeformat="%Y-%m-%dT%H:%M:%S" ctime($field$)`
wermgr_process_create_executable_file_filter	`search *`

wermgr_process_create_executable_file_filter is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Annotations

- MITRE ATT&CK

+ Kill Chain Phases

+ NIST

+ CIS

- Threat Actors

ID	Technique	Tactic
T1027	Obfuscated Files or Information	Defense Evasion

KillChainPhase.EXPLOITAITON

NistCategory.DE_CM

Cis18Value.CIS_10

APT-C-36

APT3

APT37

APT41

BackdoorDiplomacy

BlackOasis

Earth Lusca

Ember Bear

GALLIUM

Gallmaker

Gamaredon Group

Ke3chang

Kimsuky

Mustang Panda

Rocke

Sandworm Team

Windshift

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

This configuration file applies to all detections of type TTP. These detections will use Risk Based Alerting and generate Notable Events.

Implementation

To successfully implement this search, you need to be ingesting logs with the process name, parent process, and command-line executions from your endpoints. If you are using Sysmon, you must have at least version 6.0.4 of the Sysmon TA. Tune and filter known instances of wermgr.exe may be used.

Known False Positives

unknown

Associated Analytic Story

Trickbot

Risk Based Analytics (RBA)

Risk Message	Risk Score	Impact	Confidence
Wermgr.exe writing executable files on $dest$	56	70	80

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

References

Detection Testing

Test Type	Status	Dataset	Source	Sourcetype
Validation	✅ Passing	N/A	N/A	N/A
Unit	✅ Passing	Dataset	`XmlWinEventLog:Microsoft-Windows-Sysmon/Operational`	`xmlwineventlog`
Integration	✅ Passing	Dataset	`XmlWinEventLog:Microsoft-Windows-Sysmon/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: 2