implementing-anti-ransomware-group-policy

name	implementing-anti-ransomware-group-policy
description	Configures Windows Group Policy Objects to block ransomware execution and lateral spread, covering AppLocker rules, Software Restriction Policies, Controlled Folder Access, attack surface reduction rules, and network protection settings. Use when hardening Windows endpoints against ransomware via GPO, configuring AppLocker or Controlled Folder Access, or building endpoint protection policies through Group Policy.
domain	cybersecurity
subdomain	ransomware-defense
tags	["ransomware","group-policy","windows","AppLocker","hardening","prevention"]
version	1.0.0
author	mahipal
license	Apache-2.0
nist_csf	["PR.DS-11","RS.MA-01","RC.RP-01","PR.IR-01"]
mitre_attack	["T1078","T1190","T1059","T1486","T1490"]
mitre_f3	{"version":"1.1","tactics":["initial-access","positioning","monetization"],"techniques":[{"id":"T1660","name":"Phishing","tactic":"initial-access","source":"attack"},{"id":"T1219","name":"Remote Access Tools","tactic":"positioning","source":"attack"},{"id":"T1531","name":"Account Access Removal","tactic":"positioning","source":"attack"},{"id":"F1018","name":"Convert to Cryptocurrency","tactic":"monetization","source":"f3"}]}

Implementing Anti-Ransomware Group Policy

When to Use

• Hardening a Windows Active Directory environment against ransomware execution and propagation
• Implementing defense-in-depth by blocking ransomware execution paths via Group Policy
• Configuring AppLocker or WDAC rules to prevent unauthorized executables from running in user-writable directories
• Enabling Controlled Folder Access to protect critical directories from unauthorized file modifications
• Restricting lateral movement vectors (RDP, SMB, WMI) that ransomware uses to spread across the domain

Do not use as a standalone ransomware defense. GPO settings complement but do not replace endpoint detection, backups, network segmentation, and user awareness training.

Prerequisites

• Windows Server 2016+ Active Directory environment with Group Policy Management Console (GPMC)
• Domain Admin or Group Policy Creator Owners privileges
• Windows 10/11 Enterprise or Education (required for AppLocker and WDAC)
• Microsoft Defender Antivirus enabled (required for Controlled Folder Access and ASR rules)
• Python 3.8+ for audit script that validates GPO compliance
• Test OU for validating GPO settings before domain-wide deployment

Workflow

Step 1: Block Ransomware Execution Paths with AppLocker

Configure AppLocker to prevent executables from running in common ransomware staging locations:

AppLocker GPO Path:
  Computer Configuration → Policies → Windows Settings →
  Security Settings → Application Control Policies → AppLocker

Key Rules:
━━━━━━━━━
1. DENY executable rules for user-writable paths:
   - %USERPROFILE%\AppData\Local\Temp\*     (email attachment extraction)
   - %USERPROFILE%\AppData\Roaming\*         (CryptoLocker staging)
   - %USERPROFILE%\Downloads\*               (web downloads)
   - %TEMP%\*                                (temporary extraction)
   - %USERPROFILE%\Desktop\*                 (social engineering drops)

2. ALLOW default rules:
   - C:\Windows\* (signed by Microsoft)
   - C:\Program Files\* and C:\Program Files (x86)\*
   - Administrator group: all paths

3. Enable Application Identity service:
   Computer Configuration → Policies → Windows Settings →
   Security Settings → System Services →
   Application Identity → Automatic

Step 2: Enable Controlled Folder Access

Protect critical directories from unauthorized modification:

Controlled Folder Access GPO Path:
  Computer Configuration → Administrative Templates →
  Windows Components → Microsoft Defender Antivirus →
  Microsoft Defender Exploit Guard → Controlled Folder Access

Settings:
━━━━━━━━━
1. Configure Controlled folder access: Enabled → Block mode
2. Configure protected folders: Add custom paths
   - \\fileserver\shares\finance
   - \\fileserver\shares\hr
   - C:\Users\*\Documents
   - C:\Users\*\Desktop

3. Configure allowed applications: Whitelist trusted apps
   - C:\Program Files\Microsoft Office\*
   - C:\Program Files\Adobe\*
   - Line-of-business applications

Default protected folders (automatic):
  Documents, Pictures, Videos, Music, Desktop, Favorites