An Oopsie in your Firewall

So here I am, sitting at my desk post third coffee — I’m still spinning after that hardware hacking village at DefCon — and I’m thinking about something that has been bugging me for quite some time now: Misconfigured Firewalls. Not the flashy zero-day exploits, and not the cutting-edge AI-assisted threat detections. No, something far more ordinary but also far deadlier in the granular, everyday battle of network security.

Misconfigured firewalls — they’re the equivalent of the rusty brakes on your car that squeal whenever you slam on the gas but that you ignore until you barely avoid death on the highway. You never see them until it’s way too late. I’ve witnessed it up close and personal. When I was a network admin back in ’93, trying to wrangle networking gear and its nightmare PSTN for voice and data was a different kind of hell; our firewalls were primitive then — but the philosophy was sound. Fast forward: I currently operate PJ Networks, and I recently assisted three banks in migrating to a modern zero-trust environment. And guess what? At every bank, these “silent killers,” i.e., 7 firewall misconfigurations were hiding in the background universally.

The thing about network security is that a misconfigured firewall isn’t a whoopsie-daisy. It’s a breach in your fortress wall that cyber threats, large and small, use to infiltrate — sometimes without you ever realizing it.

1. Excessive Allow Rules

Here’s a little secret many companies won’t tell you: Their firewalls are full of way too many “allow” rules. More than necessary.

When I was fighting the Slammer worm in the early 2000s, it was shredding through networks with blanket allow policies on several ports. And it was devastating. Today? Same story, different worm. Too many clients, big banks I deal with, have this issue. Their rule is: “Allow anything from this IP range.” Or “Open this port so that people stop complaining.” But the result is wide-open doors.

Why is it bad?

• Blocks should be targeted but unrelated.
• Least privilege is what it says it is—don’t expose your network like a buffet.
• The more rules, the more management complexity: more opportunity for something to fall through.

Your firewall is not a bouncer in a night club. It’s a guard that checks every ID and every purpose. But many admins forget that.

2. Unrestricted Remote Access

Remote access is undeniably the lifeblood of modern workforces. But unrestricted access? That’s a recipe for disaster.

I recall one bank who had some kind of configuration where basically, remote SSH was open to the entire internet. No VPN, no multi-factor authentication — just wide-open gates. You might as well give master keys to the thieves in your building and say, Help yourself.

My advice:

• Restricting remote dedicated server access to known IPs where practical.
• Employ layered controls, such as VPNs with MFA.
• Record and audit all external sessions.

You’re otherwise playing Russian roulette with your network.

3. No Intrusion Prevention

Here’s part of the take: An Intrusion Prevention System (IPS) should not be an option; it should be a requirement.

But from what I have seen, most companies do not take IPS seriously and just focus on their firewall. Firewalls packet filter—great, but IPS looks at the traffic for malicious content. Think of it this way: Firewall is the gatekeeper, IPS is the alarm system inside your building, catching intruders that make it through the gate.

No IPS means:

• Some malware or exploits slip by undetected.
• Automated attacks are not shut down promptly.
• Detection is too little (or too late).

For those banks I recently spoke with that have implemented IPS within their firewall environments, the decision to do so has been a game-changer. Suddenly, their detection of threats wasn’t just reactive — it was proactive.

4. Weak Encryption

Oh, and don’t even get me started on encryption. It’s like the secret sauce to securing communications, but most of us get it wrong.

When I first started supervising voice/data mux systems, encryption was not very common. Fast forward and we’re just as likely to find yourself accommodating legacy weak protocols or keys because it’s too complicated, or isn’t broken.

That’s a lie.

Is it weak encryption or archaic ciphers? They’d be like a safe but with a rusted-out lock that a teenager can pick in minutes.

Here’s the advice I always give clients:

• Employ strong industry standard protocols (TLS 1.2+).
• Change encryption keys often.
• Don’t wait to kill the old stuff.

If you don’t, you’re just asking for data leakage and man-in-the-middle hassle sooner or later.

5. Outdated Firmware

Firmware updates are a pain. I get it. Downtime, testing, risks. But ignoring them? That’s akin to driving a car on bald tires and hoping for the best.

Attackers love to exploit outdated firewall firmware. Each new version fixes vulnerabilities that hackers are already taking advantage of, in the wild.

Some of my clients are still running firewalls on software so old. This complacency is waiting to explode.

Pro tip: Maintain properly

• Make a strict schedule:
• Patch firmware once security updates are confirmed.
• Promote isolation of testing environments if possible.
• Automate patches, but preserve control.

Remember: firewalls are the first defenders, and like any computing device, they improve with updates — or become a liability when they don’t receive attention.

Quick Take

For the time-impaired, here’s the short version:

• Reduce your myriad of allow rules—get surgical.
• Lock down remote access — VPN + MFA or bust.
• Don’t skimp on Intrusion Prevention—consider your layers of security, here.
• Upgrade encryption — no place for weak legacy protocols.
• There’s no excuse to not have firewall firmware kept up to date.

Ignore them at your peril.

Final Thoughts

After all these years — banging PSTN lines together and managing early network devices that supported them, all the way through running my own PJ Networks and watching the bleeding edge of zero-trust architectures happen — I can tell you authoritatively that: firewalls are not sexy. They’re just not sexy headline-generators. But they are the foundation of your network security posture.

Come closer, here is a secret — I made a lot of mistakes with firewall configs at the beginning. Giving in to convenience at the expense of security. Retrospectively embarrassing, but those lessons are what fuel what I do now.

And finally, can we PLEASE escape from the habit of blindly trusting every AI-driven firewall product? AI is good, but it cannot replace the old standbys. And no amount of fancy tech will save you if the configuration of your firewall is sloppy.

Firewall best practice and network security is personal to PJ Networks, because all of us have witnessed the carnage that incorrectly configured firewalls can cause from small businesses to high-street banks. It’s avoidable.

So the next time you take a look at your firewall, think of it as tuning your car’s brakes — not very glamorous, maybe even a little dull, but absolutely crucial for survival.

Trust me. Your network — and your sanity — will thank you.

Sanjay Seth
Cybersecurity Consultant
P J Networks Pvt Ltd