Walk around Istanbul today and you’ll still bump into the old Theodosian Walls. Twelve metres high, thick as a truck, and older than every modern nation you can name. They’re wedged between apartment blocks, half-buried under freeways, and still somehow managing to look like they could shrug off a small invasion.
Built in the 400s, these things weren’t just walls. They were a statement: Don’t even try it. Constantinople, the late Roman Empire’s shiny capital, survived more sieges than most cities have hot dinners. Huns, Avars, Persians, Bulgars all gave it a crack. All of them went home empty-handed.
Why? Because the Romans weren’t stupid enough to trust a single wall. They built three.
A moat, an outer wall, and a monster inner wall. Each one there to slow attackers, buy time, and make life miserable for anyone who thought storming the city was a good idea. It worked for a thousand years. Literally.
And here’s the kicker: that same principle still works today. Just swap swords for cyberattacks.
Defense in Depth, Roman edition
We call it “Defense in Depth” now, because everything in cybersecurity sounds fancier with a capital letter. But it’s the same idea: layers. Redundancy. Making it hard enough to get in that attackers decide it’s not worth the hassle.
So, what do your walls look like in 2025?
Moat: Strong, unique passwords. Every account gets its own key. No reusing “Password123” because it’s “easier to remember.” Get a password manager. Seriously.
Outer wall: Multi-factor authentication (MFA). Even if someone steals your password, they still can’t waltz in without your second proof - a code, your phone, your fingerprint. It’s the 21st-century castle rampart.
Inner wall: Regular, secure backups. Because one day something might go wrong, ransomware, accidental deletion, some bloke clicking the wrong link, and if it does, you’ll thank yourself for having a clean copy tucked safely away.
The real lesson
You don’t need a city of marble and mosaics to take the lesson to heart. Just a few solid layers between your business and the chaos outside the gate.
The Romans knew what many still forget: one wall, no matter how strong, eventually falls. Hackers don’t quit after one failed password, and neither should your defenses. Every extra layer turns their “easy win” into “maybe not today.”
Fifteen hundred years later, the ruins still prove the point: it’s not one wall that keeps you safe - it’s all of them working together.