# What is a security patch?

A security patch is an update from a software or hardware vendor that fixes a vulnerability. Patches arrive for operating systems, browsers, office software, firewalls, VPN gateways, printers and industrial devices. Installing them promptly is one of the most effective security measures there is, because most attacks use known vulnerabilities, not new ones. Patch internet-facing systems first, then everything else on a regular schedule. Some systems cannot be patched, such as old machines that control production; those need other protection, like a separate network segment and monitoring of what they talk to.

FAQ: [What is…? Network and security terms](https://netsenx.com/en/faq/glossary) · https://netsenx.com/en/faq/what-is-a-security-patch

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