How to remediate – WMI Firewall Enumeration

1. Introduction

The WMI Firewall Enumeration vulnerability allows an attacker with valid credentials to obtain a list of third-party firewall software installed on Windows systems. This information can help attackers identify potential targets and weaknesses in the security posture of an organisation. It primarily affects older desktop versions of Windows, such as XP, Vista, and 7. A successful exploit could lead to reduced confidentiality through reconnaissance.

2. Technical Explanation

This vulnerability occurs because Windows Management Instrumentation (WMI) allows enumeration of firewall software details via the ‘rootsecuritycenter’ and ‘rootsecuritycenter2’ namespaces. An attacker with appropriate access can query these namespaces to discover installed firewalls. This is not a direct exploit but provides information for further attacks. There is no known CVE associated with this specific enumeration, but it represents a reconnaissance risk.

• Root cause: WMI exposes firewall software details without sufficient restriction on access.
• Exploit mechanism: An attacker connects to the target Windows host using valid credentials and executes a WMI query to retrieve the list of installed firewalls. For example, they could use PowerShell to connect remotely and run Get-WmiObject -Class Win32_FirewallProduct.
• Scope: Affected platforms are Windows XP, Vista, and Windows 7 desktop operating systems. Server versions are not typically affected as these namespaces aren’t present by default.

3. Detection and Assessment

You can confirm vulnerability by checking for the presence of the relevant WMI namespaces and querying them for firewall information. A thorough method involves attempting to enumerate the installed firewalls.

• Quick checks: Use PowerShell to check if the ‘rootsecuritycenter’ namespace exists: Get-WmiObject -Namespace rootsecuritycenter. If no error is returned, the namespace is present.
• Scanning: Nessus plugin ID 10385 can detect this issue as an information disclosure vulnerability. This is provided as an example only.
• Logs and evidence: Examine event logs for WMI activity related to ‘rootsecuritycenter’ or ‘rootsecuritycenter2’. Look for successful queries from unexpected sources.

powershell -Command "Get-WmiObject -Namespace rootsecuritycenter"

4. Solution / Remediation Steps

The best approach is to limit access to the WMI namespaces or remove unnecessary software. As this vulnerability is primarily an information disclosure issue, reducing attack surface is key.

4.1 Preparation

• Dependencies: Ensure no critical applications depend on the ‘rootsecuritycenter’ namespace. A roll back plan involves restoring from the snapshot.
• Change window: This change requires a standard change window and approval from the IT security team.

4.2 Implementation

1. Step 1: Restrict access to the ‘rootsecuritycenter’ namespace using Windows Firewall with Advanced Security rules. Deny inbound connections except for trusted users or groups.
2. Step 2: If possible, uninstall any unnecessary third-party firewall software that is exposing information via WMI.
3. Step 3: Review user permissions to ensure least privilege access to WMI namespaces.

4.3 Config or Code Example

Before

# No specific firewall rule blocking access to rootsecuritycenter

After

New-NetFirewallRule -DisplayName "Block WMI Firewall Enumeration" -Direction Inbound -Namespace rootsecuritycenter -Action Block -Enabled True 

4.4 Security Practices Relevant to This Vulnerability

Practices that directly address this vulnerability type include least privilege access and reducing the attack surface.

• Practice 1: Least privilege access reduces the impact if an attacker gains credentials, limiting what they can discover.
• Practice 2: Regularly review installed software to remove unnecessary applications that may expose sensitive information.

4.5 Automation (Optional)

PowerShell scripts can be used to automate firewall rule creation and permission reviews.

# Example PowerShell script to block WMI access
New-NetFirewallRule -DisplayName "Block WMI Firewall Enumeration" -Direction Inbound -Namespace rootsecuritycenter -Action Block -Enabled True

5. Verification / Validation

• Post-fix check: Run Get-WmiObject -Namespace rootsecuritycenter again. You should receive an access denied error.
• Re-test: Re-run the initial PowerShell command from section 3. It should now fail with an access denied message.
• Monitoring: Monitor event logs for blocked WMI connections related to ‘rootsecuritycenter’.

powershell -Command "Get-WmiObject -Namespace rootsecuritycenter" # Expected output: Access Denied

6. Preventive Measures and Monitoring

Update security baselines to include restrictions on WMI access, and add checks in deployment pipelines to prevent unnecessary software installation.

• Baselines: Update a Windows hardening baseline (for example, CIS Benchmark) to include rules blocking access to sensitive WMI namespaces.
• Pipelines: Add static code analysis or configuration scanning to CI/CD pipelines to identify and block the installation of vulnerable third-party software.
• Asset and patch process: Implement a regular review cycle for installed software and apply security patches promptly.

7. Risks, Side Effects, and Roll Back

Blocking WMI access may impact applications that rely on it. The roll back steps involve removing the firewall rule.

• Risk or side effect 2: Incorrectly configured rules may block necessary system functions. Mitigation: Document all changes and have a clear roll back plan.
• Roll back: Remove the firewall rule created in step 4.2 using Remove-NetFirewallRule -DisplayName "Block WMI Firewall Enumeration".

8. References and Resources

• Vendor advisory or bulletin: No specific vendor advisory exists for this enumeration issue.
• NVD or CVE entry: No specific CVE entry exists for this enumeration issue.
• Product or platform documentation relevant to the fix: New-NetFirewallRule Documentation.