Potential Build Process Compromise - MDE

id: 1bf6e165-5e32-420e-ab4f-0da8558a8be2
name: Potential Build Process Compromise - MDE
description: |
  'The query looks for source code files being modified immediately after a build process is started. The purpose of this is to look for malicious code injection during the build process. This query uses Microsoft Defender for Endpoint telemetry.
  More details: https://techcommunity.microsoft.com/t5/azure-sentinel/monitoring-the-software-supply-chain-with-azure-sentinel/ba-p/2176463'
severity: Medium
status: Available
requiredDataConnectors:
  - connectorId: MicrosoftThreatProtection
    dataTypes:
      - DeviceProcessEvents
      - DeviceFileEvents
queryFrequency: 1d
queryPeriod: 1d
triggerOperator: gt
triggerThreshold: 0
tactics:
  - Persistence
relevantTechniques:
  - T1554
tags:
  - Solorigate
  - NOBELIUM
query: |
  // How far back to look for events from
  let timeframe = 1d;
  // How close together build events and file modifications should occur to alert (make this smaller to reduce FPs)
  let time_window = 5m;
  // Edit this to include build processes used
  let build_processes = dynamic(["MSBuild.exe", "dotnet.exe", "VBCSCompiler.exe"]);
  // Include any processes that you want to allow to edit files during/around the build process
  let allow_list = dynamic([]);
  DeviceProcessEvents
  | where TimeGenerated > ago(timeframe)
  // Look for build process starts
  | where FileName has_any (build_processes)
  | summarize by BuildParentProcess=InitiatingProcessFileName, BuildProcess=FileName, BuildAccount = AccountName, DeviceName, BuildCommand=ProcessCommandLine, 
  timekey= bin(TimeGenerated, time_window), BuildProcessTime=TimeGenerated
  | join kind=inner(
  DeviceFileEvents
  | where TimeGenerated > ago(timeframe)
  | where InitiatingProcessFileName !in (allow_list)
  | where ActionType == "FileCreated"  or ActionType == "FileModified"
  // Look for code files, edit this to include file extensions used in build.
  | where FileName endswith ".cs" or FileName endswith ".cpp"
  | summarize by FileEditParentProcess=InitiatingProcessParentFileName, FileEditAccount = InitiatingProcessAccountName, FileEditDomain = InitiatingProcessAccountDomain, FileEditUpn = InitiatingProcessAccountUpn, 
  DeviceName, FileEdited=FileName, FileEditProcess=InitiatingProcessFileName, timekey= bin(TimeGenerated, time_window), FileEditTime=TimeGenerated)
  // join where build processes and file modifications seen at same time on same host
  on timekey, DeviceName
  // Limit to only where the file edit happens after the build process starts
  | where BuildProcessTime <= FileEditTime
  | summarize make_set(FileEdited), make_set(FileEditProcess) by timekey, DeviceName, BuildParentProcess, BuildProcess, FileEditAccount, FileEditDomain, FileEditUpn
  | extend HostName = tostring(split(DeviceName, ".")[0]), DomainIndex = toint(indexof(DeviceName, '.'))
  | extend HostNameDomain = iff(DomainIndex != -1, substring(DeviceName, DomainIndex + 1), DeviceName)
entityMappings:
  - entityType: Host
    fieldMappings:
    - identifier: HostName
      columnName: HostName
    - identifier: DnsDomain
      columnName: HostNameDomain
  - entityType: Account
    fieldMappings:
    - identifier: FullName
      columnName: FileEditUpn
    - identifier: Name
      columnName: FileEditAccount
    - identifier: UPNSuffix
      columnName: FileEditDomain
version: 1.1.0
kind: Scheduled