Spyware: A general term for a class of software that monitors the actions of a computer user. This software falls into a number of categories: Software that may be installed legitimately to provide security or workplace monitoring. Software with relatively benign purposes, which may be associated with marketing data collection. In addition, software that is maliciously installed, either as a general violation of a user’s privacy or to collect information to allow further attacks on their computer or online transactions.

Keylogger: A computer program that captures the keystrokes of a computer user and stores them. Modern keyloggers can store additional information, such as images of the user’s screen. Most malicious keyloggers send this data to a third party remotely (such as via email).

Malware: “Malicious software”; a generic term covering a range of software programs and types of programs designed to attack, degrade or prevent the intended use of a network. Types of malware can include viruses, worms, Trojans, malicious active content, and denial of service attacks. In the case of invasion of privacy for the purposes of fraud or the theft of identity, software that passively observes the use of a computer is also malware (“spyware”).

Tracking Cookies: A Tracking Cookie is any cookie used for tracking users' surfing habits. Tracking Cookies are a form of Tracking Technology. Advertisers wishing to analyze and mange advertising data typically use them, but they may be used to profile and track user activity more closely. However, tracking cookies are far more limited in their ability to track users than software that is actually installed on users' computers. While installed software can potentially record any data or activity on a computer, cookies can only record visits or activity on a single website or its affiliated sites. Moreover, unlike Tracking Software, cookies entail no substantial effect on computer reliability, security, or speed.

Tricklers: Automatic Download Software designed to covertly install or reinstall software by downloading slowly in the background so the download is less noticeable. Tricklers are used to enable a spyware program to install silently or to reinstall after a user has removed components of the program from his or her computer.

Virus: Self-replicating code that propagates by reproducing and inserting itself into other programs, documents, or email attachments. Some viruses are intentionally destructive (for example, erasing information on users' hard drives). For others, the primary negative effect is their uncontrolled self-reproduction, which can overwhelm system resources.

Worm: A computer worm is a self-replicating computer program, similar to a computer virus. Unlike viruses, however, worms self-propagate and so do not require other programs or documents to spread. Worms typically spread through email or other file transmission capabilities found on networked computers.

Trojan Horse: A program that appears legitimate, but performs some illicit activity when it is run. It may be used to locate password information, make the system more vulnerable to future entry, or simply destroy programs or data on the hard disk. A Trojan horse is similar to a virus, except that it does not replicate itself. It stays in the computer doing its damage or allowing somebody from a remote site to take control of the computer. Trojans often sneak in attached to a free game or other utility (e.g.: Email).

Remote Access/Administration Tool (RAT): An executable application designed to allow remote access to or control of a system. RATs are a type of Remote Control Software. While there are many legitimate uses of RATs that do not pose security threats, they can be used maliciously by attackers to start or end programs, install and uninstall new software, or perform other potentially unwanted or unauthorized actions.

Spam: Not a virus, but is associated as computer user problem. Spam refers to electronic junk mail or junk newsgroup postings. Some people define spam even more generally as any unsolicited e-mail. In addition to being a nuisance, spam also eats up a lot of network bandwidth. Because the Internet is a public network, little can be done to prevent spam, just as it is impossible to prevent junk mail. However, the use of software filters in e-mail programs can be used to remove most spam sent through e-mail.