What is spyware?

When people talk about "spyware", most of the time they're talking about a whole range of malicious software, and not just software that actually spies on you. They usually mean anything that's installed on your PC without your knowledge or permission, and which has unwanted effects. The technical term for most of these things is usually "browser parasites", since most of them interact with Internet Explorer in some way, but in this document we're going to call them by the catch-all term malware.

Doxdesk.com describes browser parasites as follows:

"Parasite" is a shorthand term for unsolicited commercial software - that is, a program that gets installed on your computer which you never asked for, and which does something you probably don't want it to, for someone else's profit.

The parasite problem has grown enormously recently, and many millions of computers are affected. Unsolicited commercial software can typically:

• plague you with unwanted advertising ("adware")
• watch everything you do online and send information back to marketing companies ("spyware")
• add advertising links to web pages, for which the author does not get paid, and redirect the payments from affiliate-fee schemes to the makers of the software (such software is sometimes called "scumware")
• set browser home page and search settings to point to the makers' sites (generally loaded with advertising), and prevent you changing it back ("homepage hijackers");
• make your modem (analogue or ISDN) call premium-rate phone numbers ("dialers")
• leave security holes allowing the makers of the software (or, in particularly bad cases, anyone at all) to download and run software on your machine
• degrade system performance and cause errors thanks to being badly-written
• provide no uninstall feature, and put its code in unexpected and hidden places to make it difficult to remove

We're not going to be talking about actual viruses here, or traditional "trojan horse" backdoor packages. That sort of thing is adequately handled by existing antivirus software. Also note that we're only talking about Windows here. Malware is not currently a problem for either the Mac or Linux/FreeBSD users, mainly because nobody bothers to write similar programs for those platforms.

More spyware questions

• How does spyware get on my computer?
• What easy-to-use tools exist to help me get spyware off of my computer?
• What other tools exist to aid me in manually removing spyware?
• How do I prevent spyware from getting on my computer in the first place?