Suspicious parentprocess relationship - Office child processes.

id: 5ee34fa1-64ed-48c7-afa2-794b244f6c60
name: Suspicious parentprocess relationship - Office child processes. 
description: |
  The attacker sends a spearphishing email to a user. The email contains a link, which points to a website that eventually presents the user a download of an MS Office document. This document contains a malicious macro. The macro spawns a new child process providing initial access. This detection looks for suspicious parent-process chains starting with a browser which spawns an Office application which spawns something else.
severity: Medium
status: Available
requiredDataConnectors:
  - connectorId: MicrosoftThreatProtection
    dataTypes:
      - DeviceProcessEvents
queryFrequency: 1h
queryPeriod: 1h
triggerOperator: gt
triggerThreshold: 0
tactics:
  - InitialAccess
relevantTechniques:
  - T1566.002
query: |
  let browsers = dynamic(["iexplore.exe", "chrome.exe", "firefox.exe", "msedge.exe"]); // Customize this list for your environment.
  let officeApps = dynamic(["winword.exe", "excel.exe", "powerpnt.exe"]); // Consider adding other Office applications such as Publisher, Visio and Access. 
  // This is an allow-list of the most common child processes. This is a quick and dirty solution. Consider allow-listing the full process path instead of file name.
  // Also, make this list as short as possible. Remove anything from this list if it doesn't occur in your organization. 
  let allowList = dynamic(["MSOSYNC.exe", "splwow64.exe", "csc.exe", "outlook.exe", "AcroRd32.exe", "Acrobat.exe", "explorer.exe", "DW20.exe", 
  "Microsoft.Mashup.Container.Loader.exe", "Microsoft.Mashup.Container.NetFX40.exe", "WerFault.exe", "CLVIEW.exe"]); 
  DeviceProcessEvents
  | where InitiatingProcessParentFileName in~ (browsers) and InitiatingProcessFileName in~ (officeApps) and 
  FileName !in~ (officeApps) and FileName !in~ (browsers) and FileName !in~ (allowList)
  | project-rename ProcessStart_Timestamp = Timestamp
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: 1.0.1
kind: Scheduled