Immunity from the Pop-Up Plague

One lesson from the Internet bust: If something seems too good to be true, it probably is. Take those thousands of pieces of "free" software available on the Net for everything from file sharing and instant messaging to e-mail and calendar applications. The catch? Many come with code or components that allow companies to track your surfing habits, profile your shopping preferences, and sell that data to unprincipled marketers. They can also hijack your browser start page or alter important system files -- all without your knowledge.

The problem could get a lot worse. On Sept. 5, District Judge Gerald Bruce Lee ruled that Gator, a company whose software plasters its own pop-up ads and banners over any that might be contained on a Web site, was legal. But he admitted it's annoying. "Alas, we computer users must endure pop-up advertising along with her ugly brother 'spam' as a burden of using the Internet," Judge Lee wrote in his final ruling. "Ultimately, it is the computer user who controls how windows are displayed on the computer desktop."

UNDERCOVER AGENTS. It sure doesn't feel like that sometimes. Ad-ware like Gator's GAIN network -- which displays various forms of pop-up ads based on the types of Web sites you've visited before and what you click on -- can seriously slow your computer. There have been reports that it can even cause computers to crash. Its more insidious cousin, spyware, which covertly gathers personal information, usually for advertising purposes, can keep track of e-mail addresses and passwords, monitor every keystroke, even dial 900 numbers on the sly, leaving you to pay the price.

Computer experts fear that the Gator ruling will embolden less reputable software firms to bundle or just plain sneak their software onto unsuspecting users' PCs. Already, there's plenty of evidence that programmers are finding ever-more devious ways to spy on cyber-surfers.

Take Bulla, a so-called Browser Help Object for Internet Explorer. Bulla is downloaded through a malicious pop-up window, searches all the pages viewed, and replaces banner ads on the site you're visiting with those from its server, according to doxdesk.com, a site that keeps an up-to-date list of computer parasites. Bulla downloads itself surreptitiously if you visit certain Web sites with malicious pop-up ads.

Another program, ClientMan, which was bundled with some versions of popular file-sharing service Grokster earlier this year, adds advertising links to Web pages, opens pop-ups, and redirects search-engine results, all the while collecting details from e-mail, Instant messenger, and pager accounts.

SEARCH AND DESTROY. The law says it's your responsibility to guard against such privacy invasions. Maybe you didn't manage to read the 10,000-word, written-in-legalese license agreement, but that excuse doesn't fly. And you can't rely on traditional antivirus software. Outfits such as Symantec and McAfee have been hesitant to jump into antispyware software. Like Judge Lee, they know that adware and even some spyware are disclosed in multipage license agreements that consumers often blindly sign. And they don't want to tramp on the rights of legitimate companies -- such as Gator.

There are, however, several simple software programs to help you scan and destroy both pesky adware and sinister spyware. Two of the most popular are Ad-Aware, published by Swedish firm Lavasoft, and Spybot Search & Destroy from German firm PepiMK Software's. Both work much like an antivirus tool. You can set them up to scan when you boot the computer or request only manual checks. After scanning, the programs will show suspicious files and programs in red and give you the chance to delete them. Both programs also make backup copies before deleting any files, just in case you change your mind or discover that software you like to use is "ad supported" by a program such as Gator's GAIN.

Spybot and Ad-Aware are available for free. You can also pay $27 for the Ad-Aware "plus" version, which includes a memory scanner that constantly checks your PC for new spyware invasions.