What are Computer Viruses?
A brief look at the genus and species of bugs that infect your drives
So what exactly is a virus, and how is the term virus related to all those other words we hear? A virus is a program that can invade your computer to execute itself as well as replicate itself. All of these aspects make computer viruses very similar to organic viruses in that organic viruses can invade your body, they have an internal program that is activated once they invade, and they can reproduce so that they can invade bodies similar to yours.Worms
A virus needs to be attached to another executable program. A worm does not. A worm is self-contained.
The first worm was created in 1988, as an experiment to gauge the size of the internet. The problem with the program (and how it became maleficent) was that it could replicate itself. This resulted in it slowing down users computers by hogging their RAM; today this same principle is used by hackers to cause denial of service for major computer networks.
Because the worm does not need to attach itself to other programs it can propagate itself more rapidly. Anti-virus software blocks worms from your computer so you may never hear of them.Trojan
The one good thing about this type of program is that it does not possess the means to spread or replicate itself. So technically it is not a virus, although it performs some of the same functions.
Also called a Trojan horse, this type of program usually comes hidden inside another program that seems to be beneficial. You may download a free game from an internet site, but the program will come with spyware or a backdoor function that allows others to remotely use your computer.
Malware Malware is the general name for all software that has malicious intent, including all of the above and more.What can viruses do?
At their worst, they can invade your hard drive and wipe it clean then spread themselves through e-mail or other connection to any computer with which you are connected. Again, the analogy to an organic virus is apt: computer viruses can wipe out a population.
They can also do many less spectacular things such as slow down your system. They can spread themselves by invading the contact list on your e-mail program. They can disguise themselves as part of your operating system and become very hard to isolate and destroy.