Start What is updating virus definitions

What is updating virus definitions

NOTE: Using robot software to mass-download the site degrades the server and is prohibited. These files (there may be only a single file for some scanners) contain the patterns that they use to identify viruses.

If you don't already have Microsoft security software, or you want to reinstall it, see our software download page.

Windows will automatically download and install updates once a day for you.

The definition files tell the scanner what to look for to spot viruses in infected files.

Most scanners use separate files in this manner instead of encoding the virus patterns into the software, to enable easy updating.

Some programs actually update not only the virus definition files, but also parts of the scanner program itself (a program patch) when you update the virus definitions.

This is sometimes required when a new virus type necessitates a change in how scanning is done by the software.

It is critical that you update your scanner's virus definition files on a regular basis: preferably each month, but no more than every three months if monthly is impossible.

A scanner that is out of date will still find older viruses (and to be fair, many of them have been around for ages) but will leave you unprotected against newer menaces.