Network Access Control (NAC): Why It Matters for Ransomware Defense

Quick Take

• Network Access Control (NAC) prevents unauthorized devices from accessing your network.
• Ransomware moves quickly – NAC prevents lateral movement.
• Implementation matters. A poorly thought-out NAC deployment is better than nothing.
• Zero Trust + NAC = A solid defense strategy.

What is Network Access Control?

Back in the early ‘90s when I started as a network admin, the world was much more straightforward. In that world, you had a closed network, physical security was a bigger issue, and the greatest threats to the network came from configuration errors, not ransomware crippling businesses.

Now things have changed. Devices are everywhere. Shadow IT is a concern. And the expectation that everything should “just work” creates vulnerabilities due to a lack of security checks.

Here’s the thing: NAC solves that.

At its core, NAC is all about governing who and what is allowed access to your network. More than that, it manages what they can access once they’re in.

What NAC Does

• Authentication & Authorization: Confirms devices and users prior to granting entry.
• Posture Validation: Verifies security compliance of the device—OS patched, antivirus current with no sketchy software.
• Segmentation: Ensures access is based on need-to-know principles. NAC ensures that if a device shouldn’t communicate with your finance servers, it won’t.
• Security Replay: Identifies issues, investigates unauthorized access, and escalates potential security risks.

If a device fails any of these checks, it doesn’t get in. Period.

How NAC Prevents Ransomware

I’ve deployed NAC solutions for banks, enterprises, and government agencies — and from experience, I can say it’s highly effective in stopping the spread of ransomware.

What Happens Without NAC:

1. One compromised device: For example, an employee clicks on a phishing email or downloads an infected file.
2. Ransomware executes: The ransomware scans for vulnerable devices, open ports, and unpatched servers.
3. Lateral movement: Ransomware spreads, encrypts file shares, takes over domain controllers, and causes widespread disruption.

With NAC:

• Compromised devices are quarantined immediately. If a machine starts behaving abnormally, NAC restricts its network activity, stopping infections from spreading.
• Blocks unverified devices. Unauthorized devices, such as personal laptops or IoT devices, are prevented from gaining access to the network.
• Microsegmentation contains threats. Even if an infected device connects, it cannot access critical systems like databases or backups.

We witnessed this firsthand in a financial institution we assisted in adopting Zero Trust architecture. Ransomware affected two devices, but the devices were contained on a restricted VLAN that had no access to core systems. The result? What could have been a disaster was reduced to a mild inconvenience.

Implementation Best Practices

Convinced about NAC? Good. Now let’s discuss how to implement it effectively because a bad deployment can lead to vulnerabilities.

Follow These Best Practices:

1. Go all-in on Zero Trust
   • Treat everything as a potential threat until verified.
   • Network location (internal vs. external) should never dictate trust.
2. Implement Role-Based Access & Microsegmentation
   • Use strict access levels. Finance, for instance, should never have access to DevOps servers.
   • Minimize the blast radius. A hacked device should not compromise the whole network.
3. Monitor continuously
   • NAC isn’t a set-and-forget solution.
   • Regularly monitor logs, check for anomalies, and address potential risks proactively.
4. Automate responses
   • Automatically isolate any device that triggers security policies without waiting for manual intervention.
   • Leverage integration with firewalls, endpoint detection, and SIEM tools for real-time response.
5. Prepare for exceptions but avoid over-relaxing security
   • Legacy systems might not support modern security measures, so create exceptions wisely.
   • Too many exceptions can weaken your security framework. Reassess your architecture if needed.

PJ Networks’ NAC Solutions

Here’s how we can help:

• If your network permits excessive lateral movement, leaving you vulnerable to ransomware.
• If your security team is overwhelmed with alerts and struggles to control access.

At PJ Networks, we specialize in implementing tailored Network Access Control solutions. We’ve worked with businesses like banks and enterprises to make NAC the cornerstone of their ransomware defense strategy.

We deliver:

• Granular access controls that ensure only appropriate devices and users connect to your network.
• Zero Trust principles at every layer to mitigate internal and external threats.
• Automated threat responses to immediately quarantine infected devices.

With over 20 years of security expertise, we provide pragmatic solutions — not theoretical security concepts.

Conclusion

NAC might not be flashy or overly hyped, but it’s essential. Without strict controls on access and segmentation, ransomware can easily spread across your organization, causing significant harm.

• Prioritize segmentation to limit ransomware spread.
• Adopt robust access controls to safeguard your systems.
• Stop trusting internal networks without verification.

Ransomware is no longer just a technical issue — it’s a business survival issue. Network Access Control is one of the most effective ways to stop ransomware dead in its tracks. If NAC isn’t working effectively in your organization, now is the time to act — before you’re forced to by a ransomware attack.