What is a Virus (or a Worm or a Trojan)?
All of these can be called Malware, or Malicious software. A virus is a computer program or code that replicates itself and infects another program, boot sector, partition sector, or document that supports macros, by inserting itself or attaching itself. A worm is a program that copies itself from one disk to another by e-mail or other transport mechanism. Worms infect computers, but do not infect files. They can simply be identified and then deleted. However, they often make registry or startup file changes so that they are executed on boot-up. They are now very sophisticated, can avoid detection by antivirus programs and even disable them (and firewalls), so that you may have no protection whatsoever. It is probable that a lot of spam is sent out from such infected computers, unknown to the owner of the machine. A trojan is a program that neither replicates nor copies itself; it may arrive in an e-mail, in a program, or by simply viewing a web page (if your browser has an unpatched v
