How a Cloud Firewall Might Save You From Costly Breaches

Sanjay Seth, Cybersecurity Consultant, P J Networks Pvt Ltd
Real Stories Behind the Desktop

I’m drafting this post following my third coffee of the day, which, if you ask me, is just the right amount to get hyped and yet remain sharp enough to not be useless. As someone who started in the trenches back in ’93, when I was a network admin wrangling PSTN voice and data muxing, I’ve seen quite a lot. The Slammer worm? Oh, I remember that disaster directly. It traveled faster than gossip in a small town.

Now fast forward to today, and I run my own security outfit — P J Networks and recently finished securing three banks with their zero-trust architectures. I just returned from DefCon, where the hardware hacking village had me buzzing (more on this another time). But there’s one aspect of cloud security that even today is where I see the most missteps—and mistakes that result in expensive breaches.

So, if you want to keep your cloud firewall close, read on. Let’s break it down.

Cloud Firewall Basics

So let’s start from the start — you could be old school like me and remember perimeter firewalls as giant bricks that control how traffic moves into the network and out at the edge. Cloud firewalls? Consider them the firewallesque next-gen blockades that will literally be inside your cloud environment directing north-south traffic and east-west traffic though your cloud resources.

Unlike those old-school metal firewalls I’d come to learn, cloud firewalls are software-defined, elastic, and live within your cloud provider’s infrastructure. But the devil is in the details because they only work as designed if set up correctly.

Benefits of using a cloud firewall What is a cloud firewall?

• It only accepts and allows permitted traffic (based on IPs, ports, protocols)
• Denies all other traffic by default (there’s your default deny folks)
• Enforces segmentation within your cloud environment to limit lateral movement for attackers — that is, don’t give the bad guys a large area map to freely roam.

Without this? You might as well leave your digital front door wide open and put up a sign that says Help Yourself.

Cloud Misconfigurations: The Usual Suspects

Cloud firewall misconfigurations are a disease. Actually, I would bet that over 70% of the breaches we have, they’re due to some misconfiguration.

Here’s a short story: A mid-sized bank we recently evaluated had a management port left open in their cloud firewall because “we needed quick access.” That tiny slip? It was an invitation for cybercriminals. Repairing that cost a whole lot more than a couple of extra minutes spent walking through firewall rule sets.

Some common misconfiguration sins:

• Inbound rules too general rule — “Eh, let’s just open this port up to the whole internet. No. No. No.
• Keep default allow all settings in place (don’t mom, don’t do that, end of story)
• Not cleaning up rules regularly – Firewalls turn into graveyards of old (and forgotten) rules.
• Not accounting for cloud provider-specific firewall policies — do not lift-n-shift legacy rules from on-prem without adaptation
• Policies that forget identity — more on this coming up.

Here comes my own rant: Password policies mean nothing if your firewall allows any cocky bastard to trouble-shoot directly on admin ports without MFA. Your firewall is your fortress gate, sure—but password policies are your last line of defense. Both have to work together.

Identity-Based Rules

This is where I get a bit excited—identity-based rules are a paradigm shift but still so criminally underused.

This characteristic differs from traditional firewalls, which filter against IPs and ports. But in the cloud? Your resources are dynamic—IPs change, VM spin up and down. So how do you adapt? Identity-based rules bind policies to users, roles, or service accounts instead of dumb IP addresses.

Your firewall now integrates cloud identity and access management (IAM) enforcing:

• Data Availability: User Identity Verification Before Access
• Permission-limited, just-in-time access
• Context-aware policies (e.g., block if user connection is not from corporate VPN)

I’ve helped three banks roll this out personally—zero-trust without identity-aware network controls are like building a castle without gates—trust me.

Network Segmentation

It might be tempting to do nothing more than define a few rules and move on, but segmentation can be the secret sauce that keeps you out of the lateral movement attacks the vast majority of the time you get compromised, where attackers move from one compromised system to others in your environment.

Your cloud environment is like your favorite stew. If you simply dump all the ingredients in a single pot and cook it all together as a large batch, any spoiled bit renders the entire dish uneatable. But if you use separate pans with tight lids — rather than one big cooking pot — problems stay contained.

This is how effective segmentation looks in cloud firewalls:

• More separation of environments: prod, dev, test, with rules (folder and deployment) about how they can talk.
• Control traffic between VMs or containers precisely: Micro-segmentation
• A deep understanding of how to use Security Groups or NSGs (Azure/AWS) — adding rules rigidly is not the answer, find your workflow and trust zones.
• Active monitoring of east-west traffic — the traditional firewall only looks at north-south, but lateral movement is equally lethal.

In the PSTN days, if a bad voice channel came in that was frankly a pain in the neck, sure. But damage remained contained because networks were physically segmented. Today, poorly segmented cloud networks allow attackers to wander around as though they’re at a buffet.

Compliance Considerations

All right, compliance — a headache sometimes, a lifesaver other times. Whichever camp you are in, it matters. PCI-DSS, HIPAA, regional data protection laws – Banks, healthcare companies, even SMBs face regulations.

When it comes to security in the cloud firewall, compliance typically means:

• This too, all the firewall rules would enforce segregation of duties
• Displaying audit trails of who has changed what and when, in your rulesets

Common tools to help mitigate these items (there are more and all are open-source!)

• Regular audit/review of configurations (you will be audited)
• Aligning policies with regulator guidance — particularly for data-in-transit and management interfaces

P J Networks has assisted clients through multiple audits by developing firewall rulebooks and validated configuration-as-code approaches (so that you can version control your rules and get back in control).

My advice? Don’t view compliance as just checking a box — it’s a framework that, if taken seriously, does help prevent breaches.

Quick Take

• The cloud firewalls are not set and forget. They require round-the-clock surveillance.
• No blanket allow all policies. Default deny—always.
• Use identity-based rules, linked to IAM; IP-only rules are ancient news.
• Thompson, who can divide his cloud resources like his favorite recipe, separate pots for separate issues.
• Look for compliance requirements — they are your friend. Use them as a whip to force good security habits.
• Most breaches? Due to misconfigurations, not zero-day exploits.

Wrapping up

I’ve been around long enough to know that this damn field changes day to day but some fundamentals hold true. Such as setting up a proper cloud firewall. It’s not sexy. It’s not glamorous. But it’s foundational.

And the new shiny AI-powered firewall solutions have their place—all too often overselling automation and underdelivering on good design and discipline. Believe me, I know, because here’s the truth: You can’t set it and forget it. The security of your cloud firewall depends on you, the detail-oriented person who understands — and in some cases, is going to need to get their hands dirty.

For those running firewalls on cloud environments that are actually still using legacy on-prem rules UNADAPTED—well, your playing with fire. And as someone who’s extinguished a few fires in my day (metaphorically and literally), it’s a place you don’t want to be.

To help businesses like yours close these gaps before breach notifications land in your inbox, P J Networks offers assistance. Need help? You know where to find me.

Now, where’s my fourth cup of coffee?

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—Sanjay Seth
Cyber Security Consultant | P J Networks Pvt Ltd
Protecting the networks of today with experience hardened in the fields of yesterday.