Trusted Developer Utilities Proxy Execution

Status: available
Severity: medium
Time window: 1h
Source: github.com/Azure/Azure-Sentinel

This detection looks at process executions - in some cases with specific command line attributes to filter a lot of common noise.

MITRE ATT&CK coverage

Tactic	Techniques
Stealth	`T1127` Trusted Developer Utilities Proxy Execution

Telemetry coverage

Platform	Record / event type
Microsoft Defender for Endpoint	`DeviceProcessEvents` action `any`: Process activity

Rule body

id: 5c2bb446-926f-4160-a233-21e335c2c290
name: Trusted Developer Utilities Proxy Execution
description: |
  This detection looks at process executions - in some cases with specific command line attributes to filter a lot of common noise.
severity: Medium
status: Available
requiredDataConnectors:
  - connectorId: MicrosoftThreatProtection
    dataTypes:
      - DeviceProcessEvents
queryFrequency: 1h
queryPeriod: 1h
triggerOperator: gt
triggerThreshold: 0
tactics:
  - DefenseEvasion
relevantTechniques:
  - T1127
query: |
  let Timeframe = 1h;
  DeviceProcessEvents
  | where Timestamp > ago(Timeframe)
  | where (FileName has_any ("msbuild.exe", "msxsl.exe")
  or (FileName has_any ("vbc.exe","csc.exe","jsc.exe") and ProcessCommandLine has_any ("/exe","/dll","/pe64","-exe","-dll","-pe64"))
  or (FileName == ("ilsasm.exe") and ProcessCommandLine has_any ("out","target","t:","reference","r:")))
  // Filter initations by Visual Studio since this is expected behavior.
    and not(FolderPath startswith "C:\\Program Files (x86)\\Microsoft Visual Studio" 
    or InitiatingProcessFolderPath startswith "C:\\Program Files (x86)\\Microsoft Visual Studio" 
    and (InitiatingProcessFileName == "devenv.exe" or InitiatingProcessFileName == "WDExpress.exe"))
entityMappings:
  - entityType: Host
    fieldMappings:
      - identifier: FullName
        columnName: DeviceName
  - entityType: Account
    fieldMappings:
      - identifier: Sid
        columnName: AccountSid 
      - identifier: Name
        columnName: AccountName
      - identifier: NTDomain
        columnName: AccountDomain
  - entityType: Process
    fieldMappings:
      - identifier: CommandLine
        columnName: ProcessCommandLine
version: 1.0.0
kind: Scheduled

Stages and Predicates

Parameters

let Timeframe = 1h;

Stage 1: `source`

DeviceProcessEvents

Stage 2: `where`

| where Timestamp > ago(Timeframe)

Stage 3: `where`

| where (FileName has_any ("msbuild.exe", "msxsl.exe")
or (FileName has_any ("vbc.exe","csc.exe","jsc.exe") and ProcessCommandLine has_any ("/exe","/dll","/pe64","-exe","-dll","-pe64"))
or (FileName == ("ilsasm.exe") and ProcessCommandLine has_any ("out","target","t:","reference","r:")))
  and not(FolderPath startswith "C:\\Program Files (x86)\\Microsoft Visual Studio" 
  or InitiatingProcessFolderPath startswith "C:\\Program Files (x86)\\Microsoft Visual Studio" 
  and (InitiatingProcessFileName == "devenv.exe" or InitiatingProcessFileName == "WDExpress.exe"))

Exclusions

The rule actively suppresses these predicates.

Field	Kind	Excluded values	Search
`InitiatingProcessFileName`	eq	`WDExpress.exe`	`excludes:InitiatingProcessFileName` `field:"InitiatingProcessFileName" value:"WDExpress.exe"`
`InitiatingProcessFileName`	eq	`devenv.exe`	`excludes:InitiatingProcessFileName` `field:"InitiatingProcessFileName" value:"devenv.exe"`
`InitiatingProcessFolderPath`	starts_with	`C:\Program Files (x86)\Microsoft Visual Studio`	`excludes:InitiatingProcessFolderPath` `field:"InitiatingProcessFolderPath" value:"C:\Program Files (x86)\Microsoft Visual Studio"`
`FolderPath`	starts_with	`C:\Program Files (x86)\Microsoft Visual Studio`	`excludes:FolderPath` `field:"FolderPath" value:"C:\Program Files (x86)\Microsoft Visual Studio"`

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`FileName`	eq	`ilsasm.exe`	`field:"file_name" kind:eq value:"ilsasm.exe"`
`FileName`	match	`csc.exe` transforms: `term` `jsc.exe` transforms: `term` `msbuild.exe` transforms: `term` corpus 2 (kusto 2) `msxsl.exe` transforms: `term` `vbc.exe` transforms: `term`	`field:"file_name" kind:match`
`ProcessCommandLine`	match	`-dll` transforms: `term` `-exe` transforms: `term` `-pe64` transforms: `term` `/dll` transforms: `term` `/exe` transforms: `term` `/pe64` transforms: `term` `out` transforms: `term` `r:` transforms: `term` `reference` transforms: `term` `t:` transforms: `term` `target` transforms: `term`	`field:"CommandLine" kind:match`