• Posted by: Eng. Donya Bino
• February 11, 2026

Group Policy for Network Security

GPO (Group Policy Object) is one of the most effective, but also underused, tools for providing security to Windows networks as well as providing centralized control over a large number of different settings across Domains, Sites and Organizational Units (OU's). If correctly configured GPOs can enforce your organizations’ minimum security baselines, provide a smaller attack surface and help your organization comply with legal requirements.

Many organizations’ post-mortems of breaches or penetration tests show that their GPO's were poorly implemented or not in place. The 2024-2025 ransomware wave (LockBit, BlackCat/ALPHV successors) have consistently made use of poor GPOs as their ways to get into organizations and create havoc (uncontrolled PowerShell access, SMBv1 legacy enabled, weak password policy, no endpoint protection).

Importance of Group Policy for Network Security
The purpose of implementing a Group Policy Object (GPO) is to ensure consistency at scale across all computers in an organization. Without a GPO, however, endpoints can deviate from their intended configuration. Local administrators can enable risky local features (e.g. not installing local antivirus), end-users can download unverified/unapproved software on to their computer, making it easy for an attacker to gain access to the organization’s network.

The security-related advantages of having GPOs include:
1. Least privilege & Hardening
2. Blocking Entropy Attacks (native executables, credential harvestings)
3. Requiring Implementation of Required Security Controls (FW Rules, Endpoint Protection, BitLocker Disk Encryption)
4. Reducing Human Error & Deviation From Expected Configuration

GPO Network Security Recommended for High-Impact Use
These are the best practical approaches to minimizing the impact of common attack methods against systems.
1. Limit PowerShell Execution
a. Computer Settings: policy settings → administrative settings → windows components → Windows PowerShell
1) Script Execution should either be Restricted, or All Signed to execute scripts.
2) PowerShell should enable Script Block Logging and Module Logging.

b. PowerShell is also used in ~90% of all attacks , Using Constrained Language Mode with Log will help to identify instances of misuse or abuse of PowerShell.

2. Disable Legacy Protocols & Features
a. Computer Configuration → Policies → Administrative Templates → Network → Workstation/Server
1) Disable SMBv1 (always).
2) Require SMB signing (both client/server).

b. Computer Configuration → Policies → Windows Settings → Security Settings → Local Policies → Security Options
“Network security: Restrict NTLM: Incoming NTLM traffic” → Deny all domain accounts (or audit first).
c. SMBv1 and NTLMv1 are still exploited in lateral movement (e.g., EternalBlue remnants).

3. Endpoint Protection & Firewall Mandates
a) Deploy Microsoft Defender for Endpoint policies via GPO (or Intune hybrid).
b) Enable Windows Firewall in all profiles → block inbound except required ports.
c) Computer Configuration → Policies → Administrative Templates → Windows Components → Microsoft Defender Antivirus → Turn off real-time protection → Disabled.
d) Many breaches succeed because Defender was disabled locally.

4. Credential & Account Security
a. Computer Configuration → Policies → Windows Settings → Security Settings → Account Policies → Password Policy
Enforce strong complexity, 90-day max age, 14-character minimum.
b. Security Settings → Local Policies → Security Options
1) “Interactive logon: Do not display last user name” → Enabled.
2) “Network access: Do not allow storage of passwords and credentials for network authentication” → Enabled.

c. Weak passwords + credential dumping (LSASS access) remain top initial access vectors.

5. Blocking, Methods for, Living Off The Land Binaries
a. Use AppLocker Or Windows Defender Using GPO Policies Create Policy To Deny Executing Of Cmd.exe Powershell.exe, Regsvr32.exe Etc. Except From Trusted Locations
b. Attackers Use Native Tools To Avoid Detection.

6. Hardening RDP, Remote Access
a) Require Network Level Authentication NLA
b) Restrict RDP to specific groups or IP ranges.
c) Enable “Require use of specific security layer for remote (RDP) connections” → SSL (TLS 1.2+).
d) RDP remains a top ransomware entry point.

Scenarios and Lessons
1. Ransomware Attack of 2025: The organizations affected by the ransomware attack from LockBit had used GPO misconfigurations to gain access to the entire network of their companies (using PowerShell unrestricted, and SMBv1). However, organizations that had established baseline GPO would have prevented the initial execution or slowed the spread.

2. Many firms that are local to their region are utilizing a hybrid Active Directory and cloud model (Azure AD Connect). The majority of GPOs that are available, are for on-premises based products only. To provide full coverage of hybrid environments, organizations will now require hybrid join/Intune policies.

3. Compliance Considerations: GPOs can help an organization to demonstrate compliance by proving that they have controls in place for Data Protection Legislation.

Ways to Improve Your GPO
1. Auditing of Current Policies: Utilizing the Group Policy Management Console (GPMC) you can analyze an organization's Group Policy by generating a Group Policy Result (gpresult /r) or RSOP.msc on sample workstations.

2. Generation of a Security Baseline GPO: Create a Security Baseline GPO and link it at the domain level. You will then need to override it when linking it to the OU's of your servers/workstations.

3. Test Before Deploying: Create a test OU for the GPO that you tested, apply and enforce the GPO, and monitor the Event Viewer (Security logs, PowerShell logs).

4. Enable Advanced Auditing: GPO - Computer Configuration - Policies - Windows Settings - Security - Advanced Audit Policy Configuration.

5. Regular Review: Conduct GPO reviews every quarter, and utilize tools such as the Microsoft Policy Analyzer to verify that there is no drift from policy to implementation.

6. Combine with Modern Tools:  Hybrid GPOs + Microsoft Intune for cloud-managed devices.

Strong GPOs are a force multiplier for network security, centralized, auditable, and hard to bypass locally. In today's threat landscape, they remain one of the most cost-effective controls for reducing zero-day and living-off-the-land risks.