Worms & Viruses

Worms, Viruses and Trojans

Trojan: A program, usually undesirable, that pretends to be desirable program.
(http://wombat.doc.ic.ac.uk/foldoc/foldoc.cgi?Trojan+horse)
Virus: A program designed to infect other programs by copying itself into the them.
(http://wombat.doc.ic.ac.uk/foldoc/foldoc.cgi?virus)
Worm: A program that propagates itself over a network, reproducing itself as it goes.
(http://wombat.doc.ic.ac.uk/foldoc/foldoc.cgi?worm)

Worms, viruses and trojans all fall into the heading of malware. Malware could be described as any computer program that you don’t really want running on your system. It includes the category of spy-ware and possibly even pop-ads and ad tracking software.

Trojans

Trojans may arrive on your system as an email attachment or they may be downloaded from a web site. The best defense against trojans is to always know the source of the program that you are about to execute. In the case of an email attachment, know the person that sent it to you and have them verify that they did actually send you the program and that it is what it is supposed to be. Better yet, just do not run a program that comes to you as an email attachment. When you go to download a program from a web site make sure you are dealing with a reputable web site.

Worms

Worms crawl around the internet. They may arrive as an email attachment or they maybe programs that are running on another system that can access your system via a network (local or internet). A worm will usually carry one or more programs with it, called the payload. In general the payload of a worm will be a virus.

Viruses

We all know about viruses. We all fear them and eventually we will all have our computers infected with one. A virus can travel in many ways. They may be disguised as a trojan, an attachment to an email or the payload of a worm.