The Critical Role of Firewalls in Cybersecurity and Common Misconfigurations

So here I am, third coffee of the day in hand, staring at the blinking cursor and pondering how firewalls — those seemingly simple gatekeepers — are frequently the weakest link in an organization’s cybersecurity stack. I’ve been in the game since 1993, typeface network admin out of the gates screwing with muxes and PSTN, and believe me nobody survives a knock down drag out with Slammer worm in tact, or without hard earned wisdom for the trouble.

I now operate P J Networks Pvt Ltd, where we set all your firewall configs as tight as you like to block wannabe hackers in their tracks. Just returned from DefCon, where I came away even more than usual with a buzz about why, after doing recently some work for three banks on their transition to zero trust architecture, proper firewall configurations are not to be negotiated.

So here’s my deep dive into the most prevalent and dangerous firewall misconfigurations I encounter — and how you rectify them (without losing your mind). Your firewall is only as strong as the rules and logs running on it. Let’s dive in.

1. Open Ports: The Welcome Mat for Attackers

Alright, nothing infuriates me more. Firewalls are supposed to allow nothing but the required through. But what do I see? Companies leaving dozens of ports exposed like an all-you-can-eat buffet for attackers. Some with SSH running on default ports — such as 22 — with no limits. The other is the people with RDP or database ports open on the internet with no filters.

The thing is, every open port is an invitation. And unlike your grandma’s front door, there’s no polite RSVP on this invitation.

Done that — early 2000s I remember a client that had the database port open on the firewall. Slammer worm was nothing compared to what could be allowed to get through today if you are not careful.

Fix it now:

• Disable and close all unused ports.
• Connect to services using port knocking or via VPN tunnels rather than directly.
• Apply a tight IP whitelist to contain who can hit those ports.

Don’t think of open ports as equivalent to a car that locks by default. Just pretend it’s left wide open every time.

2. Lax Access Controls — The Keys to the Castle in the Wrong Hands

Access control is all about who gets to do what, and it is absolutely amazing how many people get this wrong. I’ve witnessed firewall admin panels available with a mere password (and not a good one) on the internal side. (Yeah, internal doesn’t mean secure.) And many admins even still use static IPs or, worse, allow users to manage firewall rules without proper supervision.

There’s a hard reality at play here: if you have poor access controls, then anyone inside can, effectively, get to the keys to the kingdom.

What I noticed personally in working with banks upgrading to zero-trust environments is just how important role-based access control (RBAC) is. You wouldn’t give a 16-year-old the ignition keys because you know they’re careful, right?

How to lock it down:

• Apply robust multi-factor authentication (MFA) even for in-house firewall management.
• Employ RBAC to restrict who can alter firewall rules or access logs.
• Regularly review user permissions – people change, and leave, and so on.

Otherwise, you’re driving your network with the keys under the doormat.

3. The Default for Too Long — Cybersecurity’s Open Door Least Pickable Policy

Sigh. This still happens. Default credentials are the cyber equivalent of leaving your car running whilst you rifle through a shop for two minutes, it’s not hard, there’s just no provision made for the fact that people will actually do it. I’m pretty sure there are a lot of people who think clicking next next finish through a setup wizard saves time but is expensive in the long run.

I’ve audited firewalls that had the admin password still as admin or pass123. It is laughable; Any child could make this type of exploit even with limited understanding.

It’s not a best practice. It’s the only way.

Fix this now:

• Dropping default usernames and passwords is past due.
• And, for heaven’s sake, please don’t choose an easy-to-guess password. No, Password1 is not complex.
• Utilize a password manager to create and store strong and unique passwords.

Side rant: password policies can be insane. I am leery of imposing 30-day password changes on users — it’s a hassle and usually encourages them to choose weaker ones. Instead consider length and complexity and MFA.

4. No Logs — Flying Blind in a Cyberstorm

Without logging retrieved firewall events, you’re flying blind, Hess said. I would even call it malpractice. Some companies believe firewall logs are noisy and simply disable them, or they set the thresholds so high that nothing ever alerts.

But logs are your front line and evidence when things go sideways.

In one project involving a financial client, it took weeks to detect a breach because the firewall logs were missing. Costly mistake.

Logging best practices:

• Enable logging for all firewall rule matches, denied connections, and administrative changes.
• Collect logs centrally with SIEM tools to have better correlation.
• Analyse logs regularly to detect any abnormalities.

No logs? No insights. No insights? No security.

5. No Rule Audits – The Perishing Of The Firewall Diet

Firewall rules are just like recipes, if you keep adding ingredients without tasting, your dish becomes a disaster. But a lot of orgs just pile on rules and rules. The rules multiply over the years, some become obsolete, and nobody dares to clean up.

The result is complexity, slow performance and massive cyber risks. Learn from my experience — when we audited the firewall of a large bank, we found hundreds of active rules that 30% between them had never triggered but through traffic.

Rule audits are essential.

Perform regular firewall rule audits like you would engine tuning on a race car leading up to a big race — eliminate dead rules, fix duplicated or conflicting rules, and tighten up those exceptions.

Audit checklist:

• Revisit rules every quarter (or more often when feasible).
• Delete all the unused or unwanted rules.
• Write down the reason and rule changes.
• Try your rules in a staging environment before going live.

Ignoring this? You have a rusty iron brake system and you have no idea when it is going to go.

Quick Take

• Close all the unneeded open ports ASAP.
• Apply tight access controls with MFA and RBAC.
• Use of default credentials is a big no-no, changing them on day one.
• Enable logging and review the logs periodically.
• Audit your firewall rules and make them lean and mean.

Wrapping Up

Firewalls are not magic boxes, they are complex rule engines and require constant care and attention. To treat them like a set and forget device is a recipe for disaster. For all my decades on the front line — from buzzing PSTN lines to today’s zero-trust banks — I’ve found that people, processes, and persistent attention are what will keep your network safe long after any fancy marketing buzzwords or AI-powered tooling has lost its lustre. (Seriously, I’m suspicious of any approach that relies too heavily on AI without human checks.)

Just keep in mind: the effectiveness of your firewall doesn’t come from the number of rules it has, but from the quality of those rules and how they are managed and monitored. And if you’re perplexed or overwhelmed, that’s where people like me at P J Networks come in to clean up the mess.

The worst time to consider firewalls is after a breach. It’s now or never, because after attackers drop in through a service opened up by sloppy configs, it’s not as simple as clicking buttons when the house is on fire.

Ok, enough ranting for one morning. Time for coffee number four?