What is Malware? By: Miek Gall

We use the term at Sirius Solutions to describe software that may be installed on your computer you would most likely not want if you knew it was there or what it was doing. A formal definition:

(n.) Short for malicious software, software designed specifically to damage or disrupt a system, such as a virus or a Trojan horse.

Virus
Most of us are familiar with this term, and are thankful for the tools available to help prevent infection. There are many types of viruses, some that hurt a little, others that hurt a lot! As with the human variety, these little bundles of code will automatically try to replicate themselves.

Trojan Horse
You may have heard of this as described by Homer in his classic "Iliad". The Greeks used a large wooden horse to trick the Trojans, and win the city Troy as a prize. These pieces of code can be thought of as viruses with two important distinctions: 1) they do not replicate themselves; and 2) they often hide themselves by pretending to be something else, like a benign screensaver software download (viruses are often disguised too!)

Adware
Stealth advertising components that are installed by some "shareware" products (and sometimes, legitimately purchased commercial software) and may collect personal information from your computer, like name, address, or surfing patterns. Generally, this information will be used to influence "popup" advertisements based on what they have discovered about you. Certain software is classified as Adware simply because a large portion of the application screens contain advertising messages.

Spyware
Pretty much the same as adware, don't get caught up in the lingo they refer to the same class of application. Stealth components and background processes that may violate your privacy or expose your computer to attack.

"Backdoor Santa's"
Non-stealth "freeware" and shareware apps that may transmit personal information or expose your computer to attack, under the pretense of providing a useful service.

Homepage Hijackers
Once one of these nasty ad-Trojans worms onto your system, it will constantly reset your homepage (and maybe Search, etc.) to where they want you to go. You can't change it back!

Foistware (Everything-installs-it-can't-get-rid-of-it)
Unwanted application programs that come along, trojan-style, with completely unrelated software. Usually because some jerk is getting paid to foist it on your system whether you want it or not. Since they tag along with so many different pieces of third-party software, it is not uncommon to get re-infected with these foistware products again and again.