What is an attack surface?

The attack surface is everything an attacker could try to use to get in: internet-facing servers, VPN gateways, email accounts, remote access tools, cloud services, staff phones and laptops, suppliers with access, and even unused open ports. The bigger it is, the more there is to defend. Reducing it is often cheaper than defending it: switch off services nobody uses, close remote access that is open to the whole internet, remove old accounts and limit supplier access. A good first exercise is listing what you expose to the internet; the list is usually longer than people expect.

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