What is the difference between a computer virus and spyware?
Okay, I like to work with analogies, so look at it this way. Spyware and viruses (or virii) are two different beasties. Sometimes they blur the lines between each other, but generally it's a case of apples and oranges.
Take for example: Spyware is like your sleazy uncle. He wheedles himself into your house, eats your food, fouls up the plumbing and staggers in a 3 AM with a couple of his drunken buddies. Stuff will disappear from your house, but nothing really big. The change jar in your kitchen will slowly dwindle down and you'll get phone calls from salesmen that your sleazy uncle told to call you. Sure, your sleazy uncle says, you'd LOVE to buy a diesel grease powered recliner chair!
He's annoying, he tells people stuff about you that you don't want them to know, he uses your stuff and makes your life much more annoying, but that's about it.
Viruses on the other hand, are like a band of angry, hungry Vikings. A virus will bust in, with horned helmets, rob you blind, destroy your stuff, hurt you in ways you didn't know possible, use your house as a base of operations to launch attacks against your friends and neighbors, then in the last action of pure spite, burn down your house in a blazing night time pyre.
Compared to a virus, spyware is a bastion of morality and goodness.
Now don't me wrong. Spyware can bring in other malicious programs, who bring in worse programs until you wake up one morning and find that what started with your sleazy uncle has wound up with you walking into the bathroom and finding some guy named Hrothgar using your toothbrush. When one domino falls, the rest are sure to follow.
Now, as to the nature of the two beasties.
First, are you protected? Sure! You proclaim. I've got $AntiVirus Product X! I'm safe. Three words: no you ain't. First off, $AntiVirus Product X is designed to protect you against viruses. Spyware, your sleazy uncle, has more plaque built up than the guy who taste-tests the burger company's french fries. End result? Your computer is so slow it's nearly useless. And as for the $AntiVirus Product X? Sure, it was 'da bomb' last decade, but today it's something of a joke. Younger, more aggressive companies who want to be king of the hill have made $AntiVirus Product Z2008 which makes the one you have look like the old guy who used to hold the 'stop' sign for you when you walked to grade school. $AntiVirus Product Z2008 is Chuck Norris; you own Barney Fife. Do some research when buying your anti-virus. Don't just grab the one off the shelf that the dork in the black tie and the pimply face has been told by his corporate masters to push of on you, the unsuspecting public.
The way a virus scanner works goes something like this: the virus scanner has been written to recognize generalities. A computer virus has a certain 'look' to it. There are new types of viruses cropping up every now and then, but for the most part all new viruses are just variations on a theme. Your virus scanner has a rough sketch of what the virus looks like. The virus scanner company releases updates (for the love of mike: update your scanner) which make the sketch clearer and tells the scanner the likely places the virus will hide. This is one case where the axiom of “information is power” is paramount.
So, armed with this information, your virus scanner sallies forth to fight the good fight. Make sure you pick the current version of Sir Lancelot, not Don Quixote. Do some research. Read some reviews. Seriously; would you trust your life to the White Knight?
Now, as to spyware, it's an altogether different situation.
The makers of anti-spyware programs have to know EXACTLY what they are looking for. No generalities are used in the spyware business. The people that make anti-spyware stuff have many researchers, pouring over new information coming in from all corners of the globe. They then must decide if the program, and that's what spyware consists of, is malicious in intent. Your computer picks up things called cookies all the time. It's a way a website can remember who you are It's useful when you want to quickly log back in to a site you go to often. When a website uses that information for malice, such as following around the Web, that is where it can turn sleazy.
Thus, your anti-spyware software has to be updated probably even more often than you would think. New sites pop up every day and spyware purveyors are like dandelions. If you slack off just for a while, your lawn will be covered in yellow.
In the end, it comes down to prevention and vigilance. Choose a good anti-virus and a good anti-spyware. Some companies claim to make a product to cover you in all cases, but just because a company makes a great refrigerator doesn't mean they can make a good cell phone. Choose well. Follow the instructions. Be vigilant. Update.
And stay away from MySpace.
That is another story though...