What are the kinds of viruses out there, how do they get in your computer, and where they come from?

Really need help on this please. Also can you get viruses from messenger or in some sites like asian west.

Thanks a lot for your answers.

What are the kinds of viruses out there, how do they get in your computer, and where they come from?windows

Types of virus

From worms to macros, there's a whole host of viruses out there to catch...

Worms

These viruses spread via computer networks. The ILOVEYOU virus above was a classic example of a worm. These viruses are becoming an increasing threat as a growing number of computers are permanently connected to networks. Worms can spread over corporate networks or via emails sent over the Internet.

Trojans

A Trojan virus takes its name from a story in Homer's Iliad where Greek soldiers pretended to make peace with their enemies, the Trojans. The Greeks made a grand peace-keeping gesture - the gift of a large wooden horse.

When the Trojans hauled it inside their city gates, a small band of Greek warriors leapt out. They opened the gates and let the rest of the Greek army storm in to capture the city.

A Trojan virus is one that opens your computer up to malicious intruders, allowing them to read your files.

File viruses

A file virus is one that replaces a key system file on your computer. These viruses can reload themselves every time you start your computer up. Once they're in the memory, they can spread by writing themselves to any disk you insert into your disk drive.