Detection: Suspicious MSBuild Rename

Description

The following analytic detects the execution of renamed instances of msbuild.exe. It leverages data from Endpoint Detection and Response (EDR) agents, focusing on process names and original file names within the Endpoint data model. This activity is significant because msbuild.exe is a legitimate tool often abused by attackers to execute malicious code while evading detection. If confirmed malicious, this behavior could allow an attacker to execute arbitrary code, potentially leading to system compromise, data exfiltration, or further lateral movement within the network.

Search

1
2| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime from datamodel=Endpoint.Processes where Processes.process_name!=msbuild.exe AND Processes.original_file_name=MSBuild.exe by Processes.action Processes.dest Processes.original_file_name Processes.parent_process Processes.parent_process_exec Processes.parent_process_guid Processes.parent_process_id Processes.parent_process_name Processes.parent_process_path Processes.process Processes.process_exec Processes.process_guid Processes.process_hash Processes.process_id Processes.process_integrity_level Processes.process_name Processes.process_path Processes.user Processes.user_id Processes.vendor_product 
3| `drop_dm_object_name(Processes)` 
4| `security_content_ctime(firstTime)` 
5| `security_content_ctime(lastTime)` 
6| `suspicious_msbuild_rename_filter`

Data Source

Name	Platform	Sourcetype	Source
CrowdStrike ProcessRollup2	N/A	'crowdstrike:events:sensor'	'crowdstrike'
Sysmon EventID 1	Windows	'xmlwineventlog'	'XmlWinEventLog:Microsoft-Windows-Sysmon/Operational'
Windows Event Log Security 4688	Windows	'xmlwineventlog'	'XmlWinEventLog:Security'

Macros Used

Annotations

Default Configuration

This detection is configured by default in Splunk Enterprise Security to run with the following settings:

Implementation

The detection is based on data that originates from Endpoint Detection and Response (EDR) agents. These agents are designed to provide security-related telemetry from the endpoints where the agent is installed. To implement this search, you must ingest logs that contain the process GUID, process name, and parent process. Additionally, you must ingest complete command-line executions. These logs must be processed using the appropriate Splunk Technology Add-ons that are specific to the EDR product. The logs must also be mapped to the Processes node of the Endpoint data model. Use the Splunk Common Information Model (CIM) to normalize the field names and speed up the data modeling process.

Known False Positives

Although unlikely, some legitimate applications may use a moved copy of msbuild, triggering a false positive.

Associated Analytic Story

• BlackByte Ransomware

• Cobalt Strike

• Graceful Wipe Out Attack

• Living Off The Land

• Masquerading - Rename System Utilities

• Trusted Developer Utilities Proxy Execution MSBuild

References

• https://lolbas-project.github.io/lolbas/Binaries/Msbuild/

• https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1127.001/T1127.001.md

• https://github.com/infosecn1nja/MaliciousMacroMSBuild/

Detection Testing

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: 9