Attack surface
Also called external attack surface, internet exposure, exposed systems
Every point where an outsider can try to get into a system or get data out of it: login pages, open ports, APIs, test servers.
An attack surface is everything about a system that an attacker can touch from where they stand. For most organisations the part that matters first is the external one: whatever can be reached from the internet without already being inside.
It grows quietly. A cloud server started for a test, a remote-access tool installed for one contractor and an admin page left open after a migration all add to it, and none of them appears on the diagram.
AI has changed how quickly it gets found. Mapping what an organisation exposes used to take an attacker time, which gave obscure systems some cover. Agents now do that mapping and compare what they find with known flaws. So knowing your own attack surface is the first step in deciding what to patch, and making it smaller is often quicker than patching.
For example
A firewall's management page that can be opened from any internet connection is part of your attack surface. Restricted to the office network, it isn't.
Put it to use
Where you'll meet attack surface in ChatGPT, Gemini and Claude, how to use it there, and the mix-up most people make.
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