Adware

Program that creates advertisments on your Pc.

Note that many websites have their own advertising, unrelated to adware.

Official definition:
"Adware is any software application in which advertising banners are displayed while the program is running. The authors of these applications include additional code that delivers the ads, which can be viewed through pop-up windows or through a bar that appears on a computer screen. The justification for adware is that it helps recover programming development cost and helps to hold down the cost for the user.
Adware has been criticized for occasionally including code that tracks a user's personal information and passes it on to third parties, without the user's authorization or knowledge."

Browser Hijacker

Program that changes some settings in your browser.

Commonly:
- Changing your "search" page to pass all searches to a certain pay-per-search site
- Changing your default home page to the company page (most of often porn sites)
- Transmitting URLs viewed toward the company server

Browser Plugin

This category contains mostly dubious browser plugins such as "Search Assistant"s, toolbars etc. that have been known to transmit user data to their creators.

Commercial Keylogger

Program designed to monitor user activity. May be used with or without consent.

Commercial Network Management Tool

Tools of this kind are mostly used in (large) coorperations. They can log network traffic passively (sniffing) or examine the logs of proxies etc. Nothing is installed on the individual computers, the software runs on a central server, They can only log things that pass thru the network, not local things like entered passwords, keystrokes or screenshots.

Dialer

A program that (secretly) changes your dialup connection setting so that instead of calling your local internet provider, your Pc calls some very expensive 0900 or international phone number.

Generic Malware

Generic category for all unwanted software that secretly executes unwanted actions

Remote Adminstration Tool

A tool that is intended to be used by network administrators to remotely control a PC on the network, usually for support or inventory purposes.

Due to the nature of the program, the possibility exists to be exploited for spying purposes.

Trojan

A hacker tool that is secretly installed on your Pc and that allows the attacker to get almost complete over your computer.

Virus

Malware that spreads itself automatically by infesting other files on your Pc

Official description:
"Software which attaches to other software. A boot virus inserts its code into the boot record or master boot record of a disk, so that when the machine boots from that disk, the virus code is executed. A file virus inserts its code into an executable file, so that when that file is executed, the virus is executed as well. A macro virus attaches itself to documents like Word or Excell."

Worm

Virus-like program that spreads automatically to other computers, by sending itself out by email or by any other means.

Official description:
"A program that propagates itself by attacking other machines and copying itself to them. Both worms and viruses are self-replicating code that travels from machine to machine by various means. Both worms and viruses have, as their first objective, merely propagation. Both can be destructive, depending on what payload, if any, they have been given. But there are some differences: worms may replace files, but do not insert themselves into files. In contrast, viruses insert themselves in files, but do not replace them."