splunk-security_content/docs/_posts/2021-01-12-suspicious_msbuild_path.md

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title	excerpt	categories	last_modified_at	toc	toc_label	tags
Suspicious msbuild path	Masquerading, Trusted Developer Utilities Proxy Execution, Rename System Utilities, MSBuild	Endpoint	2021-01-12	true		Masquerading Defense Evasion Trusted Developer Utilities Proxy Execution Defense Evasion Rename System Utilities Defense Evasion MSBuild Defense Evasion Splunk Enterprise Splunk Enterprise Security Splunk Cloud Endpoint

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Description

The following analytic identifies msbuild.exe executing from a non-standard path. Msbuild.exe is natively found in C:\Windows\Microsoft.NET\Framework\v4.0.30319 and C:\Windows\Microsoft.NET\Framework64\v4.0.30319. Instances of Visual Studio will run a copy of msbuild.exe. A moved instance of MSBuild is suspicious, however there are instances of build applications that will move or use a copy of MSBuild.

• Type: TTP
• Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
• Datamodel: Endpoint
• Last Updated: 2021-01-12
• Author: Michael Haag, Splunk
• ID: f5198224-551c-11eb-ae93-0242ac130002

ATT&CK

ID	Technique	Tactic
T1036	Masquerading	Defense Evasion

| T1127 | Trusted Developer Utilities Proxy Execution | Defense Evasion |

| T1036.003 | Rename System Utilities | Defense Evasion |

| T1127.001 | MSBuild | Defense Evasion |

Search

| tstats `security_content_summariesonly` count values(Processes.process_name) as process_name values(Processes.process) as process min(_time) as firstTime max(_time) as lastTime from datamodel=Endpoint.Processes where `process_msbuild` AND (Processes.process_path!=c:\\windows\\microsoft.net\\framework*\\v*\\*) by Processes.dest Processes.original_file_name Processes.parent_process Processes.user 
| `drop_dm_object_name(Processes)` 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)`
| `suspicious_msbuild_path_filter`

Associated Analytic Story

• Trusted Developer Utilities Proxy Execution MSBuild
• Cobalt Strike
• Masquerading - Rename System Utilities

How To Implement

To successfully implement this search you need to be ingesting information on process that include the name of the process responsible for the changes from your endpoints into the Endpoint datamodel in the Processes node. In addition, confirm the latest CIM App 4.20 or higher is installed and the latest TA for the endpoint product.

Required field

• _time
• Processes.dest
• Processes.user
• Processes.parent_process_name
• Processes.parent_process
• Processes.original_file_name
• Processes.process_name
• Processes.process
• Processes.process_id
• Processes.parent_process_path
• Processes.process_path
• Processes.parent_process_id

Kill Chain Phase

• Exploitation

Known False Positives

Some legitimate applications may use a moved copy of msbuild.exe, triggering a false positive. Baselining of MSBuild.exe usage is recommended to better understand it's path usage. Visual Studio runs an instance out of a path that will need to be filtered on.

RBA

Risk Score	Impact	Confidence	Message
49.0	70	70	Msbuild.exe ran from an uncommon path on dest execyted by user

Reference

• https://lolbas-project.github.io/lolbas/Binaries/Msbuild/
• https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1127.001/T1127.001.md

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

• https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1127.001/windows-sysmon.log

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