Viruses
A virus is a small piece of software that piggybacks on real
programs. For example, a virus might attach itself to a program
such as a spreadsheet program. Each time the spreadsheet program
runs, the virus runs, too, and it has the chance to reproduce
(by attaching to other programs) or wreak havoc.
E-mail
viruses
An e-mail virus moves around in e-mail messages, and usually
replicates itself by automatically mailing itself to dozens
of people in the victim's e-mail address book.
Worms
A worm is a small piece of software that uses computer networks
and security holes to replicate itself. A copy of the worm
scans the network for another machine that has a specific
security hole. It copies itself to the new machine using the
security hole, and then starts replicating from there, as
well.
Trojan
horses
A Trojan horse is simply a computer program. The program claims
to do one thing (it may claim to be a game) but instead does
damage when you run it (it may erase your hard disk). Trojan
horses have no way to replicate automatically. |