implementing-anti-ransomware-group-policy

name	implementing-anti-ransomware-group-policy
description	Configures Windows Group Policy Objects (GPO) to prevent ransomware execution and limit its spread. Implements AppLocker rules, Software Restriction Policies, Controlled Folder Access, attack surface reduction rules, and network protection settings. Activates for requests involving Windows GPO hardening against ransomware, AppLocker configuration, Controlled Folder Access setup, or endpoint protection via 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"]

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.

Common Misconfigurations & Verification

• GPO doesn't block the shadow-copy/recovery LOLBins: the most common gap is leaving vssadmin delete shadows, wbadmin delete catalog, bcdedit /set {default} recoveryenabled no, and wmic shadowcopy delete runnable. AppLocker path rules rarely cover these because the binaries live in C:\Windows\System32 (allowed by default). Add explicit AppLocker/WDAC deny rules or an ASR/EDR block for these signed binaries and confirm a non-admin user cannot delete shadows.
• ASR rules left in Audit mode: rules set to action 2 (Audit) log but never block. Verify AttackSurfaceReductionRules_Actions is 1 (Block) for the email/Office-child-process rules, not just configured.
• AppLocker without Application Identity service running: rules silently don't enforce if the AppIDSvc service isn't set to Automatic. Confirm the service is running, not just that rules exist.
• Controlled Folder Access protects defaults but not the file shares: UNC paths like \\fileserver\finance must be added explicitly; CFA only auto-protects Documents/Desktop locally.
• Verification: run gpresult /r on a test OU endpoint, then actually attempt the attacks — drop and run an EXE from %AppData%\Temp (expect AppLocker 8004), modify a file in a protected folder from an unlisted app (expect CFA 1123), run vssadmin delete shadows /all /quiet as a standard user and confirm it is blocked, and open a macro doc to confirm child-process blocking. Pilot on a test OU before domain-wide linkage.

Prerequisites