I recently had a rather rough introduction to the concept of 'adware', software that piggybacks on other software that you install, for the purposes of displaying advertising on your computer. Such software displays ads without giving any indication of what program is causing it, without having asked your permission to install itself, and no obvious way to uninstall it-- in some cases, it can't be uninstalled by uninstalling the program it came with.

Such a trojan horse, no better than malicious computer viruses that use similar tactics, can also take the even more insideous form of 'spyware'. This kind of software monitors your use patterns and transmits that information over the Internet to a company that processes and sells that information, all without your consent or knowledge.

I don't mind ad-sponsored software or services. If I'm explicitly agreeing to a contract where I allow ads on a web page or even a piece of software in exchange for free use, then I can consider that the cost of the software, and decide to use it or not use it based on how intrusive I find it. But this kind of adware is often dissociated with the sponsored program enough that any mainstream user would have no idea how it got there, and certainly not know how to get rid of it. I consider myself to be an advanced computer user and I had to ask in message forums what the hell it was.

Thankfully, such trechery can't go unchecked on an Internet full of smart, determined and pissed-off users. Adware, Spyware and Advertising Trojans lists offending programs and has detailed removal instructions. SpyChecker offers a database to look up software to check for known offenses. The Spyware Infested Software List is a long list of software that sends information over the Internet without your knowledge or explicit consent. The Gibson Research Corporation web site has more information on Internet traffic monitoring and ad/spyware detection.

In my case, the offending program was BearShare, a Gnutella client for Windows. Apparently I was informed of the software being installed, but it was never made clear what the software was, only that it was "required". It installed a piece of adware called SaveNow, and a browser plug-in for New.net, a company trying to usurp ICAAN's control over domain names. (I'm intentionally not linking to these due to my objections with their business models. You can look them up on your own if you like-- just don't let them install any software if they ask. :) Enough people object to this behavior that BearShare is now officially BewareShare. (I also have reason to suspect, with minor confirmation from others, that BearShare has actually modified my system in a way that makes it prone to crashing, even after uninstalling BearShare. Probably not intentional or even related, but it brings up another good point about software being installed unknown to the user: software is sometimes poorly written, and has bugs, and if you don't know what's running on your computer, it's virtually impossible to figure out how to fix problems.)

So if you're getting extra pop-up ads these days, you may be affected. SaveNow, for example, will open an ad for DealTime whenever you visit a competitor, such as Amazon.com, saying that you can get a better price somewhere else. I would think the industry at large would detest this kind of advertising, and I hope it suffers a quick and painful death.