When do I actually need to run a virus scan?

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Summary: There are two types of virus scans: continuous or periodic. Which and how many you need and how often they're needed depends on your situation.

Virus scanners are best used to prevent viruses from ever reaching your machine, but you raise a very good issue that most folks don't realize.

There are two types of scans.

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One type of scan is the continuous "real time" scan that watches for viruses in data as it arrives (or possibly as it leaves) your computer. Typically the scanner will hook into your network connection and simply watch the data coming and going to and from your machine, watching for viruses. If it sees one then it takes action and alerts you. These are definitely the safest. For example, a virus in a download will be caught before it's ever had a chance to run on your machine. Some will also prevent email-borne viruses from arriving in your inbox as well.

It's important that there be only one real time scanner running at a time, as they can conflict with each other. But one is all you need.

The other type of virus scan is an "on demand", or scheduled scan. This is when you ask your virus program to scan the contents of your hard disk for viruses. It then scans your machine, reading every file for possible viruses. Naturally reading everything on your hard drive can take a little while.

The free virus scans are typically this type. You initiate a scan, and a while later the scanner tells you whether or not your machine was infected and whether or not it was able to remove the infections.

Most anti-virus programs include both types of scans; real-time and on-demand. I advise having a couple of additional on-demand scanners ready (or at least selected) when it comes time to track down a particularly nasty virus that perhaps your regular virus scanner misses.

For what it's worth, I normally don't run a real time scan since I'm fairly well protected in other ways. I do, however, run an on-demand scan which is scheduled every night.

Critical to all this, of course, is that you make sure that the database of virus definitions your scanner uses is as up-to-date as possible. I make sure to downloading the latest database for my anti-virus software every night.

Whether you run a real-time scanner or a nightly or periodic scan, remember that it's critical to do something. The days of being blissfully ignorant about viruses is long past. Without virus protection you are setting yourself up for some serious problems down the road.

Related:

• Ask Leo! - How do I keep my computer safe on the internet?

• Ask Leo! - What's the best Pop-Up Blocker? Anti-Virus Software? Anti-Spyware Software?

• Ask Leo! - This computer's infested, what do I do?

Article 957 | Posted December 30, 2004