First let’s take a quick look at the three major categories of malware. In the biggest categorical sense, viruses and spyware represent very different basic issues.

The purpose of a software virus is to cause damage, either to your machine, or to use your machine in a coordinated attack on other machines or indeed, on the whole Internet.

Viruses can generally be stopped before they hit your machine.

Spyware Transmits Information about You

Spyware is a buzzword that has many different facets and definitions.

Spyware is unlike a virus in that its purpose is rarely mayhem but rather information gathering, which may be for legitimate marketing purposes (as discussed in a few minutes), but more often is for purposes ranging from the irritating and invasive to the downright criminal.

There are many different definitions for “spyware” out there now, but we think a simple functional definition will help you understand the problem it represents best. Some kinds of viruses – such as Trojans, which are bad programs hidden in good ones – may actually meet the definition for spyware also, so it can be a little confusing.

One widely accepted definition is a pretty good one, as used by Information Week magazine and numerous spyware websites:

Spyware is software that’s installed without your informed consent. Spyware communicates personal, confidential information about you to an attacker. The information might be reports on your Web-surfing habits, or the software might be looking for even more sinister information, such as sniffing out your credit card numbers and reporting those numbers.

That is about as good a summary as there is.

Of course while you read that definition and it sunk in, you probably started thinking “Hey wait a minute, how can that be, people can’t just drop little software bombs on my machine!”

Actually they can and they do all the time. A colleague’s computer was running slowly, in spite of good hardware, a fast processor and a T1 connection. We asked if she had run anti-spyware software and we got a quizzical look.

We loaded a couple of scanner programs and found more than 1,300 infections!

Most of these are far more irritating than they are dangerous, but they should all be dealt with, and we’ll tell you how.