What are Viruses and Why Should we use an Anti Virus Software? ( Part 2 - Computer viruses, worms and Trojans)

 This is part 2 (Computer viruses, worms and Trojans) of the discussion "What are Viruses and Why Should we use an Anti Virus Software?"

Click here to read the Part 1 (What are Viruses)

Computer viruses, worms and Trojans

What they are and what they can do?

Worms are computer programs that can copy themselves from machine to machine, extremely quickly, through computer networks.
Computer worms differ from computer viruses because they run independently and do not need a host file, boot sector or file transfer between machines to propagate.
Worms:
There are different types of computer worms that spread through various services including e-mail and instant messaging clients.

E-mail worms;
These are spread via infected e-mail messages in the form of an attachment or link to an infected Web site - some e-mail worms will also spoof e-mail addresses.

IM worms;
These are spread via instant messaging clients, to entire contact lists, in the form of links to infected Web sites.

Internet worms;
These are spread when the Internet worm scans, tries to connect and, if successful gains access to any vulnerable machines - either by scanning the Internet and/or using the local operating system.

IRC worms;
These are spread via IRC channels in the form of infected files or links to infected Web sites.

File-sharing Networks Worms;
These are spread from shared folders via the P2P network.


Continue with the next part. In the next part of this series I'm going to discuss the question "After Installing Anti Virus Software, What Should I Do?"
  
Click here to read the Part 3 (After Installing Anti Virus Software)