Encyclopedia  |   World Factbook  |   World Flags  |   Reference Tables  |   List of Lists     
   Academic Disciplines  |   Historical Timeline  |   Themed Timelines  |   Biographies  |   How-Tos     
Sponsor by The Tattoo Collection
Main Page | See live article | Alphabetical index


Strictly defined, spyware consists of computer software that gathers information about a computer user without the user's knowledge or informed consent, and then transmits this information to an external entity—usually one that expects to be able to profit from it in some way. Data-collecting programs installed with the user's knowledge do not, properly speaking, constitute spyware, if the user fully understands what data is being collected and for whom.

More broadly, the term spyware applies to a wide range of related malware products which do not constitute spyware in the strict sense. These products perform many different functions, including the delivery of unrequested advertising (pop-ups in particular), harvesting private information, re-routing page requests to illegally claim commercial site referral fees, and installing stealth phone dialers.

Table of contents
1 Spyware and viruses
2 Consequences
3 Installation
4 Solutions
5 Known spyware
6 Spyware removal programs
7 See also
8 External links

Spyware and viruses

Spyware closely resembles but clearly differs from computer viruses. In both cases, the program installs without the user's knowledge or consent. In both cases, system instability commonly results.

A virus, however, replicats itself: it spreads copies of itself to other computers if it can. Spyware generally does not self-replicate. Where a virus relies on users with poor security habits in order to spread, and spreads so far as possible in an unobtrusive way (in order to avoid detection and removal), spyware usually relies on persuading ignorant or credulous users to download and install it by offering some kind of bait. One typical spyware program targeted at children, for example, claims that:

He will explore the Internet with you as your very own friend and sidekick! He can talk, walk, joke, browse, search, e-mail, and download like no other friend you've ever had! He even has the ability to compare prices on the products you love and help you save money! Best of all, he's FREE!

The ideal piece of spyware installs itself in such a way that it starts up every time the computer starts up (using CPU cycles and RAM, and reducing stability), and runs at all times, monitoring Internet usage and delivering targeted advertising to the affected system. [1]

A virus generally aims to carry a payload of some kind: in other words, to do some some damage to the user's system (such as, for example, deleting certain files). The damage caused by spyware, in contrast, usually occurs incidentally to the primary function of the program. Spyware generally does not damage the user's data files; indeed (apart from the intentional privacy invasion and bandwidth theft), the overwhelming majority of the harm inflicted by spyware comes about simply as an unintended by-product of the data-gathering or other primary purpose.

A virus does deliberate damage (to system software, or data, or both); spyware does accidental damage (usually only to the system software). In general, neither one can damage the computer hardware itself. Certain special circumstances aside, in the worst-case the user will need to reformat the hard drive, reinstall the operating system and restore from backups. Having this done professionally typically costs in the order of US$50. The cost of lost time and productivity can greatly exceed this. It frequently happens that the owner of a badly spyware-infected system purchases an entire new computer in the belief that the existing system "has become too slow."


Unprotected Windows-based computers, particularly those used by children or credulous adults, can rapidly accumulate a great many spyware components—commonly several hundred individual instances. The consequences of a moderate to severe spyware infection (privacy issues aside) generally include a substantial loss of system performance (over 50% in severe cases), and major stability issues (crashes and hangs). Difficulty connecting to the Internet also commonly occurs.

As of 2004, spyware infection causes more visits to professional computer repairers than any other single cause. In more than half of these cases, the user has no awareness of the spyware problem and initially assumes that the system performance, stability, and/or connectivity issues were related to hardware, Windows installation problems, or a virus.

Some spyware products have additional consequences. Dialers attempt to connect directly to a particular telephone number rather than to the user's own ISP: where connecting to the number in question involves long-distance or overseas charges, this can result in massive telephone bills which the user has no choice but to pay. To further compound the situation, some telephone companies have taken advantage of the situation by charging more for dialing the locations where these scams originate. Eircom, the former state telecom operator in Ireland, has placed a number of small Pacific islands (where the scams originate) in a special 6/min tariff band. Unlike the band of special premium rate numbers, telephone subscribers cannot block these numbers.


Spyware normally install itself through one of two common methods:

  1. The spyware component lies hidden within an otherwise apparently useful program. Often, the containing program is made available for download free of charge, so as to encourage wide uptake of the spyware component.
  2. The spyware takes advantage of security flaws in Internet Explorer.

Spyware can also install itself on a computer via a virus or an e-mail trojan program, but this does not commonly happen.

The HTTP cookie, a well-known mechanism for storing information about an Internet user on their own computer, often stores an individual identification number for subsequent recognition of a website visitor. However, the existence of cookies and their use generally does not hide from users, who can also disallow access to cookie information. Nevertheless, to the extent that a Web site uses a cookie identifier to build a profile about the user, who does not know what information accumulates in this profile, the cookie mechanism could count as a form of spyware. For example, a search engine website could assign a user an individual ID the first time he visits and store all search terms in a database with this ID as a key on all subsequent visits (until the cookie expires or is deleted). This data could be used to select advertisements to display to that user, or could—legally or illegally—be transmitted to third parties.

Granting permission for web-based applications to integrate into ones system can also load spyware. These browser helper objects embed themselves as part of a web browser.

Spyware usually installs itself by some stealthy means. If you read the user agreement for the software you download and install, it may make references (sometimes vague) to allowing the issuing company of the software to record your internet usage and website surfing. Some software vendors allow you to buy the same product without this overhead.


Use of automatic updates (on Windows systems), antivirus, and other software upgrades will help to protect systems. Software bugs and exploits remaining in older software leave one vulnerable, because the public rapidly learns over time how to exploit unpatched systems.

A number of software applications exist to help computer users search for and remove spyware programs (see external links). Some programs purge your system of spyware, only to install their own.

Known spyware

Spyware removal programs

See also

External links