When the antivirus is outdated. It's pretty much useless. New threats that have been discovered since its last update cannot be picked up, as it'll not show any no record of it being a vulnerability. Patching your anti-virus means that it can pick up everything that it should do.

Is a patch a virus?

Win32/Patched is a computer Trojan targeting the Microsoft Windows operating system that was first detected in October 2008. Files detected as "Trojan. Win32.

What is the purpose of patching?

What is the Purpose of Patching? Patching is a process to repair a vulnerability or a flaw that is identified after the release of an application or a software. Newly released patches can fix a bug or a security flaw, can help to enhance applications with new features, fix security vulnerability.