Windows Worm Vulnerabilities: Legacy OS Risks

G5 Cyber Security

1 month ago

TL;DR

Yes, several wormable vulnerabilities remain unfixed in older Windows versions (XP, Server 2003, and even some later ones). These pose a serious risk if your systems are internet-connected. Patching is the best defence, but mitigation steps can help if patching isn’t possible. This guide details known risks and how to address them.

Understanding the Risk

Wormable vulnerabilities allow malicious software to spread automatically between computers without user interaction. Older Windows systems are particularly vulnerable because they no longer receive regular security updates, leaving these holes open for exploitation. Connecting these systems to the internet significantly increases the risk of infection.

Identifying Vulnerable Systems

Check your Windows version: Press Windows Key + R, type
```
winver
```
and press Enter. Note the ‘Version’ and ‘Build’ numbers.
Common vulnerable versions include:
- Windows XP (all service packs)
- Windows Server 2003 (all service packs)
- Windows 7 (especially without Service Pack 1)
- Windows Server 2008 (without SP1 and later updates)

Known Wormable Vulnerabilities & Mitigation

Here are some significant vulnerabilities that have affected legacy Windows systems. Note this isn’t an exhaustive list, but covers major threats.

1. MS08-067 (EternalBlue)

This vulnerability affects older versions of Windows and was famously exploited by WannaCry ransomware. Even if you don’t think you are vulnerable, check!

Check for patch status: Use the Microsoft Baseline Security Analyzer (MBSA), though it’s outdated, it can still detect this vulnerability.
```
mbsa -r -n <computername>
```
Mitigation if patching is impossible: Disable SMBv1. This is risky as some older applications may need it, but significantly reduces the attack surface.
1. Open PowerShell as Administrator.
2. Run:
```
Stop-Service -Name LanmanServer -Force
```
```
Disable-NetAdapterBinding -Name *SMBv1* -Confirm:$false
```

2. Remote Desktop Protocol (RDP) Vulnerabilities

Older versions of RDP have numerous vulnerabilities that can be exploited remotely.

Disable RDP: If not essential, disable RDP completely.
1. Press Windows Key + R, type
```
sysdm.cpl
```
  and press Enter.
2. Go to the ‘Remote’ tab and select ‘Don’t allow remote connections to this computer’.
Network Level Authentication (NLA): Ensure NLA is enabled if RDP *must* be used. This adds an extra layer of security.
```
gpupdate /force
```
(after configuring via Group Policy)

3. Server Service Vulnerability (MS04-011)

This vulnerability allows remote code execution and was actively exploited in the past.

Check patch status: Use MBSA as described above for MS08-067.
Mitigation if patching is impossible: Restrict access to port 135 using a firewall. This prevents external connections to the vulnerable service.
1. Configure your Windows Firewall or third-party firewall to block inbound traffic on TCP port 135.

General Cyber security Best Practices

Network Segmentation: Isolate legacy systems from the main network. Place them in a separate VLAN with strict firewall rules.
Firewall Rules: Implement strong firewall rules to limit inbound and outbound traffic on these systems. Only allow necessary connections.
Antivirus/Anti-malware: Install and keep updated antivirus software, although this is less effective against zero-day exploits.
Monitoring: Monitor network traffic for suspicious activity. Look for unusual connection attempts or data transfers.

Final Thoughts

Leaving legacy Windows systems unpatched is a significant cyber security risk. Prioritise patching whenever possible. If patching isn’t feasible, implement the mitigation steps outlined above to reduce your exposure. Consider replacing these systems with modern, supported alternatives if they are no longer essential.