Suspicious Msbuild Execution By Uncommon Parent Process

Status: test
Severity: medium
Log source: category process_creation, product windows
Author: frack113
Source: github.com/SigmaHQ/sigma

Detects suspicious execution of 'Msbuild.exe' by a uncommon parent process

MITRE ATT&CK coverage

Tactic	Techniques
Stealth	No specific technique

Telemetry coverage

Provider	Record / event type
Sysmon	Event ID 1: Process creation

Rule body

title: Suspicious Msbuild Execution By Uncommon Parent Process
id: 33be4333-2c6b-44f4-ae28-102cdbde0a31
status: test
description: Detects suspicious execution of 'Msbuild.exe' by a uncommon parent process
references:
    - https://app.any.run/tasks/abdf586e-df0c-4d39-89a7-06bf24913401/
    - https://www.echotrail.io/insights/search/msbuild.exe
author: frack113
date: 2022-11-17
tags:
    - attack.stealth
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        - Image|endswith: '\MSBuild.exe'
        - OriginalFileName: 'MSBuild.exe'
    filter_parent:
        ParentImage|endswith:
            - '\devenv.exe'
            - '\cmd.exe'
            - '\msbuild.exe'
            - '\python.exe'
            - '\explorer.exe'
            - '\nuget.exe'
    condition: selection and not filter_parent
falsepositives:
    - Unknown
level: medium

Stages and Predicates

Stage 0: `condition`

selection and not filter_parent

Stage 1: `selection`

selection:
    - Image|endswith: '\MSBuild.exe'
    - OriginalFileName: 'MSBuild.exe'

Stage 2: `not filter_parent`

filter_parent:
    ParentImage|endswith:
        - '\devenv.exe'
        - '\cmd.exe'
        - '\msbuild.exe'
        - '\python.exe'
        - '\explorer.exe'
        - '\nuget.exe'

Exclusions

The rule actively suppresses these predicates.

Field	Kind	Excluded values	Search
`ParentImage`	ends_with	`\cmd.exe`	`excludes:ParentImage` `field:"ParentImage" value:"\cmd.exe"`
`ParentImage`	ends_with	`\devenv.exe`	`excludes:ParentImage` `field:"ParentImage" value:"\devenv.exe"`
`ParentImage`	ends_with	`\explorer.exe`	`excludes:ParentImage` `field:"ParentImage" value:"\explorer.exe"`
`ParentImage`	ends_with	`\msbuild.exe`	`excludes:ParentImage` `field:"ParentImage" value:"\msbuild.exe"`
`ParentImage`	ends_with	`\nuget.exe`	`excludes:ParentImage` `field:"ParentImage" value:"\nuget.exe"`
`ParentImage`	ends_with	`\python.exe`	`excludes:ParentImage` `field:"ParentImage" value:"\python.exe"`

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`Image`	ends_with	`\MSBuild.exe` corpus 9 (sigma 9)	`field:"Image" kind:ends_with value:"\MSBuild.exe"`
`OriginalFileName`	eq	`MSBuild.exe` corpus 20 (elastic 15, splunk 4, sigma 1)	`field:"OriginalFileName" kind:eq value:"MSBuild.exe"`

Suspicious Msbuild Execution By Uncommon Parent Process

MITRE ATT&CK coverage

Telemetry coverage

Rule body

Stages and Predicates

Stage 0: condition

Stage 1: selection

Stage 2: not filter_parent

Exclusions

Indicators

Stage 0: `condition`

Stage 1: `selection`

Stage 2: `not filter_parent`