John IT Solutions

Viruses
No you cannot catch a virus from your computer, anyone who says that is lying and/or and idiot (Your computer's keyboard however, is one of the dirtiest places ever, along with door handles and other commonly touched objects). Now that we've got that out of the way, a computer virus is a file that attaches itself to a program or a file and waits to be transported from one computer to another. From Virus to Virus, the effects vary, as does the severity of the virus. The virus can't actually do anything unless you run the program. Also Viruses cannot be spread without human action.

Worms
Worms are a sometimes referred to as a sub-class of virus, but with one key difference, Worms can travel without human intervention, they can replicate themselves without human intervention. This means your computer could be sending out thousands of Worms, one in every e-mail, and attachment and on every memory stick. A worm might send itself to everyone in your address book, and then they would pass it on. This will eventually take up enough system memory, or network bandwidth.

Trojans
A trojan horse is a program that pretends to be useful software, such as a file converter or other form of free software. The files appear legitimate as, it shows the user what they would expect to see. Some trojans are merely to annoy the user, such as changing the wallpaper to a different image. Some more severe trojans delete or create malicious files. Worse still trojans create a back-door, meaning that malicious software can pass into your computer as if it were a back door left open, in you house.

Blended Threats
These are a mixture of two or more of the above dangers, they combine the worst bits of them together to form a