A virus usually arrives onto your computer hidden inside of another program which is often delivered by email attachments. It derives its name from the fact that just like a living virus, it needs a host to live and breed on. When you run the infected host program, you then launch the virus into the memory of your computer where it sets up home and waits to go about it's intended function of destroying your files and infecting other computers.
Once the virus has infected your computer it waits for the programmed trigger to signal it into action. The trigger coded into the virus and can be anything from a specific date to a set number of times it has replicated itself.
Once triggered, it goes about the destruction it was designed for. It may be a simple deletion of files or pranks. It could also be programmed to destroy your operating system.
Viruses are commonly spread on email attachments. This is why you should never open an attachment unless you know who it was from. The problem is that sometimes it can appear as if a virus is just an attachment from someone in your address book, so always be on alert when you get an email with an attachment on it particularly if it is an .exe file.
Worms work a lot like viruses do. They are also self replicating and can reproduce so fast that they can overload and shut down entire systems. The difference between a virus and a worm is that the worm doesn't require a host to live on. A worm is stand alone malware. They also usually hitch their way onto your computer through email but don't need an attachment to ride on.
Trojans aka Trojan horses
Trojans take their name from the classic Greek story for they misrepresent themselves as well. They often pretend to be something they are not. Trojans are not self reproducing like worms and viruses but they can do just as much damage. They hide on other programs and record your keystrokes and steal passwords and credit card numbers.
Fighting malware
It is important to stay up to date with the latest methods being used to combat malware. Your computer can be destroyed by one of these nasty computer programs or your credit card and other personal information can be compromised. For starters it is a good idea to not open email attachments to reduce your risk of picking up a virus. Use a good virus detecting program and firewall to keep the pesky bugs out of your system.
