Why Both Internal and External Security Matter

4 minute read

Some questions arrive like rain — subtle, quiet, unassuming — and yet they leave everything changed. One of those questions came to us not long ago, not from a Fortune 500 company, but from a mid-sized educational institution. The CISO leaned forward and asked, “Do we really need both an internal and an external security assessment?” His tone was cautious, skeptical even, as if the answer might unlock some unwelcome cost. Or worse — reveal something they weren’t ready to face.

The room went still. A clock ticked. And then, like peeling back the edge of a bandage, the answer began to unfold.

Let’s start inside.

In internal security assessment isn’t about spying on employees or some Hollywood fantasy of watching command centers pulse with red alerts. It’s about turning the mirror inward. Think of it as inviting someone into your home — not the living room you’ve already cleaned for guests, but the bedroom, the attic, the cluttered garage. A proper internal assessment pokes into your endpoints, your privileged accounts, your network segmentation. It’s not malicious; it’s meticulous. The goal is simple: understand what a threat actor could do once they’re already in.

Because here’s the truth: many breaches don’t begin with a spectacular explosion of firewall-breaking code. They begin with a cracked password, a forgotten server, or a staff member who clicked on a too-convincing phishing email. Once inside, it’s a quiet heist. And internal assessments ask: how far could they go if they got this far?

Then there’s the other side — the one your board of directors, your customers, your insurance provider cares about most. The external security assessment. It’s the view from the outside. The front door, the windows, the fire escape — metaphorically speaking. Here, the assessors behave like burglars scanning the perimeter. They look for exposed services, misconfigured web apps, open ports, outdated SSL protocols. They scan, they prod, they measure your digital footprint the way a storm measures a coastline.

But what people forget — what even well-meaning cybersecurity services companies sometimes fail to communicate — is that these two assessments don’t compete. They complete each other.

Internal reveals impact. External reveals exposure.

One reveals what damage can be done; the other, how likely it is to happen.

Seasoned cybersecurity consulting firms have seen it time and again. A company boasts about passing their external pentest — no open ports, all TLS 1.3, everything patched. But no one checked that five employees were using the same weak password. No one realized that MFA wasn’t enforced on the domain admin accounts. And no one looked at the fact that the company’s internal VLANs were stitched together like an open field.

So when ransomware finally comes in — via a compromised contractor’s laptop — it moves sideways like wildfire. No resistance. No segmentation. No backups that weren’t already compromised.

That’s what an internal assessment might have caught.

And then there’s the reverse. There are numbers of companies that spent years hardening their internal posture, only to discover a critical web application had a vulnerability wide open to the internet. No WAF. No rate limiting. And their subdomains? Barely monitored. One stray dev instance, still live, holding real client data. A disaster waiting to be invited.

That’s what an external assessment was made to catch.

The difference between the two isn’t just one of perspective — inside versus out. It’s a philosophical one. One asks “what if the enemy is already here?” The other asks “how strong are our gates?” You need both questions. Because real threat actors don’t care which path works — just that one does.

In the end, we told the CISO that the answer to his question wasn’t binary. It wasn’t a matter of choosing between them. It was about understanding their relationship. One makes the other meaningful. A fortress with locked gates is still doomed if it’s crumbling from within. And a palace with strong walls but no guards? Just a waiting game.

And so he nodded. Not dramatically, not immediately. But with the kind of quiet understanding that comes when you realize the storm has already been on its way.