Evolution of Endpoint Security and the Role of Firewalls in Zero Trust

I’m sitting here at my desk—3rd coffee just hit stalks!—and I’m struck by how far endpoint security has come since when I began as a network person-boy back in ’93. Man, those were the days, configuring networking and mux lines to handle voice and data over PSTN, until the Slammer worm came along and gave us a crash course on network perimeter security.

Fast forward to today — I own a cybersecurity agency, P J Networks, and I’ve just been involved in bidding on three banks modernizing their Zero Trust environment. If you believe that the term Zero Trust is just the latest buzzword, you’re sort of missing the point—and firewalls are still deeply, supremely relevant to that model, all the more so in regards to endpoint security.

Endpoint Security Basics

Let’s get one thing clear:

Your endpoint is your front line. It’s where your data resides, your apps run and where one little vulnerability could blow open your entire perimeter.

Zero Trust flips the old model — you don’t trust anything inside the network by default. Every device, every user, every packet must be authenticated. That whole “castle and moat” deal? Dead. And frankly, I’m glad. I remember spending countless hours trying to get perimeter firewalls working just right, only to learn the hard way that the attacks were coming in through endpoints that we hadn’t bothered to protect because no one thought we needed to worry about them.

The Deal with Endpoint Security

• It’s not just antivirus or EDR tools. Devices require secure, authenticated, and persistent access.
• Static allow/deny lists don’t even dent the attack surface – specific contexts are key.

I’m thinking device posture, user roles, geolocation, time of day — all rolled into your access decisions. And firewalls? They’re no longer just sitting at your network edge. They move when your endpoints do — yes, even those laptops and mobile devices on the roam.

Firewall-Based Device Access

I have this analogy I always like to throw out there: Firewalls are the bouncers standing at the nightclub door, whereas Zero Trust is like having individual bouncers who check your ID, verify you were invited, gaze your shoes for contraband and even sniff your breath for trouble. No more generic let anyone in policy, sheesh.

The great thing about modern firewalls — like those we deploy here at P J Networks — is that they mix traditional filtering rules with extremely fine grained context awareness:

• Who is the user?
• What device are they on?
• Patch status and compliance of the device.
• Where are they phoning from?

And all of this takes place before the device even gets to touch sensitive resources.

And a few banks we helped protect recently, this approach prevented rogue devices at their doorsteps. You need to plug in a personal phone or unauthorised USB? Sorry, no dice. And the firewall rules do, in fact, force identity and state of device.

Sure, a lot of people say that firewalls are so last century now, especially automated, AI-powered security. But here’s the thing: A.I. isn’t magic; it’s just a tool. And when set up properly, firewalls remain the Zero Trust world’s most faithful gatekeepers.

Restricting Unknown Endpoints

I remember in the early 2000s feeling invincible because we had all these border firewalls in place, and that we would be able to block the obviously bad actors. Then Slammer demonstrated how wrong I was, to the the entire industry. It shot indoors through openings as if they were open windows.

Today, with the rise of remote work and BYOD, endpoints that are unmanaged or incorrectly secured are now the novo attack vector. Unknown endpoints are constantly trying to connect, and the Zero Trust model says Not unless you prove you’re safe. This is where firewall-based device access is once again shining.

Here’s what I see at PJ Networks when I’m doing a client assessment:

• Rogue appliances often out of nowhere on networks
• They go undetected by most traditional network security tools
• Firewalls with built-in device posture checks identify these devices early.

And I’m not saying you can just close the door and forget about those users — the idea is to authenticate and verify every device before it comes in.

One thing I’d rant about here: Password policies alone are not the solution for this. I’ve seen giant orgs lock down password complexity while completely ignoring device-level risks such as unchecked updates or unknown apps operating in the background. Firewalls do help since they can enforce policies at the device level, not just user creds.

Threat Containment

And if a device is trusted and allowed in, does that mean that we are safe? Absolutely not.

Zero Trust says: trust nothing, assume breach. So firewalls also play a central role in isolating threats:

• Network segmentation to restrict east-west communication.
• Use least privilege for your firewall rules.
• Real time analytics to spot cheating happening.

I’ve been on the wrong side of too many incident response cases where the attacker compromised one endpoint and promptly moved laterally to vital servers and systems because firewall segmentation was lacking or nonexistent.

At DefCon this year, the hardware hacking village demo’d absolutely terrifying physical device hacks that could completely subvert software controls. Firewalls are not the be-all and end-all — no superpower here — but they are another critical layer you can use to quarantine infected devices before damage can spread.

I am asked frequently by clients if they should integrate EDR or NGAV with endpoint firewalls. My answer: Absolutely yes. But the firewall is still bedrock — EDR quite possibly be your knives and pots; maybe not think of it as the stove in the kitchen. Can cook without knives? Maybe. But you wouldn’t.

Continuous Risk Assessment

And here is where most companies fail, because security can’t be set-and-forget.

Firewalls and Zero Trust are not static. They continuously assess:

• Device health
• User behavior
• Network anomalies

And then they make the access policies dynamic. Perhaps your laptop experiences some sort of weird config change, or the user logs in from some shady location? Boom—firewall policies can isolate or escalate the authentication to require MFA.

Here at P J Networks, we employ a hybrid approach to ensure that these controls remain as keen as they were on the first day we set them up. Yes, automating is excellent, but nothing beats expert human eyes on the dashboard that can alert subtle changes in risk.

Quick Take

• Endpoints are your primary attack surface today, so secure them as though your business depends on it (because it does).
• Firewalls in Zero Trust aren’t simply about blocking; they’re about contextual gatekeeping.
• Unknown endpoints = big no no. Firewalls can help you identify them and cordon them off while they are still in their infancy.
• Containing the threat calls for intelligent segmentation and dynamic rule enforcement.
• Real-time evaluation means your firewall rules adjust instantaneously.

Conclusion

To sum up — here’s what I’ve learned over a career of three decades in the realm of networking and cybersecurity: firewalls can’t cure all, and there’s no one-size-fits-all answer to it all. But deployed properly, as part of a Zero Trust endpoint security strategy, they are absolutely indispensable.

If you are still regarding firewalls as just a perimeter gadget, please think again. They’ve evolved — and need to — as your security mindset has.

And although I’m skeptical of the endless parade of A.I.-powered silver bullets, I do believe in using technology in concert with smart, layered policies and some measure of healthy vigilance. Then, and only then, do you get anywhere near what Zero Trust supposedly delivers: never trust, always verify, and minimize damage when the worst comes to pass.

From my keyboard, buzzing with the caffeine that’s kept my tired fingers tinkering, I beg you: do not discount the lowly firewall in your endpoint defense.

Stay safe out there.

— Sanjay Seth, P J Networks Pvt Ltd