As online file traders stream to Napster alternatives, many are finding their computers saddled with unwanted piggyback software that tracks their online movements and feeds them unwanted advertising. In efforts to locate revenues from their free services, companies that create popular programs, including Bearshare, Audio Galaxy Satellite and iMesh, are adding outside pieces of software that have nothing to do with file trading. Dubbed "adware" or "spyware" by their critics, these software programs run in the background even when the original file-swapping software isn't operating, popping up advertisements while people surf online, and sometimes quietly uploading information about a Web surfer's habits. The programs have sparked a swell of protest from some people computer-savvy enough to figure out what software is running on their machines and what it is doing. But the companies defend themselves, saying there are worse alternatives and they need some revenue sources if they are to continue to offer their products for free. "One of the issues around free software is the need to make money somehow," said Vinnie Falco, chief technical officer of FreePeers, the company that created the BearShare Gnutella software. "It's a great compromise between protecting user privacy and the ability to support free software." File-swapping companies aren't alone in a scramble for revenues that is threatening to alienate some people online. The drive for personal information that might be valuable for advertising purposes has prompted several companies to offer software that collects this data and sometimes sends it back to the parent company. Although most of the companies doing this are relatively small, even larger companies such as RealNetworks have occasionally tried to keep surreptitious tabs on computer users' actions. "This is all over," said Richard Smith, chief technical officer for the Privacy Foundation. "Anytime you're downloading a piece of software, you're basically trusting the company not to do anything too bad." As file-swapping service Napster continues to decline, people are streaming to the alternative programs in record numbers, focusing a spotlight on this type of software. According to statistics kept by CNET Download.com, a software download site maintained by ZDNet News publisher CNET Networks, more than 6.8million people have downloaded Audio Galaxy's software and more than 3million have tried FreePeers' Bearshare. This represents a huge, potentially captive audience for advertisers who can somehow take advantage of these numbers. And a few are trying. The advertising software typically comes bundled with a single installation program, so there is initially no way to tell what will be installed on a person's computer. Some of the services do flag the extra software, either in the license agreement that people are theoretically supposed to read, in a separate "readme" text file, or as part of the installation process. It's rarely entirely clear what the software does, however. One of the most pervasive pieces of piggyback software is dubbed "SaveNow," created by a company called WhenU.com. Distributed along with BearShare, iMesh and the Global DivX player that allows people to watch many online movies, it tracks where a person goes online and then pops up separate browser windows with targeted advertisements or special offers. Unlike some "spyware" software, this one doesn't send information back to the company that created it. But it continually downloads updated information about new offers and keeps a record of where a person surfs on that person's own computer. It runs continually--even when the program it came with is not operating. Another similar program is distributed with Audio Galaxy. Created by a company called Gator, the "Offer Companion" is slowly downloaded to a person's computer after Audio Galaxy is installed and eventually starts sending information such as e-mail addresses and Web surfing habits back to Gator.com. It also pops up advertisements as people surf. This is an optional feature with Audio Galaxy. People who don't want it must pay close attention when first installing the service, or the ad software will be downloaded automatically. The advertising software has prompted some discussion on bulletin boards online and drawn criticism from people who say the extra programs are privacy violations and can hurt computer performance. "SaveNow is buggy and tends to screw up your network connection," Manish Vij, a BearShare user and founder of Web design firm NetStudio, said. "Every time I launch a browser, SaveNow keeps trying to run and makes my network connection flaky." People can check what kinds of software might be running in the background without their knowledge by checking the Windows Task Manager, which is started by pushing the Alt, Tab and Ctrl keys all together. More information on other piggyback programs can be found several places online, including Cexx.org. Privacy experts caution that people should be aware of what they are downloading and where it is from, particularly if it is a piece of software. They say companies need to do a better job of warning their customers what will be installed on their computers. "I think this really breeds mistrust across the industry," the Privacy Foundation's Smith said. "I think companies need to be more forthcoming." See techTrader for technology investment news, plus quotes and research. Have your say instantly, and see what others have said. Click on the TalkBack button and go to the techTrader forum Let the editors know what you think in the Mailroom. And read what others have said.