Computer security used to be relatively simple. It was more a matter of talking people into using the available tools -- antivirus and antispyware software -- and then keeping them up to date. The latest generation of online malice, though, is harder to track. It comes via code that might be added to an innocent Web site. As you read the site, your PC suffers an upload of "bot" software and soon becomes a "zombie," pumping out spam e-mail behind the scenes.

Maybe your antivirus software finds the bot, but maybe not, because some malware writers are sophisticated enough to disable such programs. You go about your daily computing tasks and notice only a few glitches. The PC is unexpectedly sluggish, perhaps, or your browser seems unstable. In the background, the bot software is checking in with home base, a Web server that runs the network -- "botnet" -- of hijacked machines to mine your data or spread spam.

How big a problem are botnets? Vinton Cerf, inventor of the TCP/IP protocols that drive the Internet, said recently that of the 600 million computers connected to the Net, 150 million might be unwitting members of a botnet.

So today's security isn't just a matter of using software tools.

By now, if you have a high-speed connection, you know that a firewall is essential. But the firewall loophole is that programs downloaded through the browser go right through, which makes these surreptitious uploads hard to stop. The premium is now placed on keeping your browser up to date with the latest software patches, something that the major operating systems make easier to do than before.

The botnet idea might one day be turned against malicious software.

Harvard computer specialist Jonathan Zittrain is talking about "herd computing," in which a large number of computers automatically upload information about their health. Instead of reporting to a malicious bot server, the herd computers would call in with problems relating to any software they had recently downloaded.

Herd computing could be a great solution for spyware and a satisfying way to turn a malevolent use of technology into one that benefits everyone.

But while we wait for such advances, the old advice still applies.

Keep your security software up to date, use a firewall and heed your operating system's warnings about downloading updates. The clever ways of Internet data harvesters are a daily threat, but if you do these things, you drastically reduce the chances of being compromised. And we can look forward to the day when PCs all over the planet collaborate on benevolent nets to protect us from the bots.

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Pandora.com is an outrageously addictive Internet music service.

I was about to recommend it anyway when it suddenly sprang into the news. First came word that Pandora, along with other Internet radio companies, would face a hugely inflated fee structure, courtesy of the Copyright Royalty Board. Then came the news that the service would become unavailable to international listeners because of complications related to paying rights-holders in individual countries.

But first things first.

You want to listen to Pandora because it lets you create your own "station," a playlist that learns from your preferences and gets better over time. The first step with this free service is to choose an artist you like -- I chose jazz pianist Bill Evans.

Pandora then serves up music not only by that artist but by others that it deems are like him or her. So Bill Evans was followed by McCoy Tyner, Herbie Hancock, Oscar Peterson. With each piece, you click to give a thumbs up or down, and pretty soon all thumbs are up.

This seems like a brilliant marketing strategy for musicians, because it exposes listeners to many artists whose work they might not have heard and offers unheard material from their favorites, as well.

But the very idea of Internet radio is threatened by the upcoming changes to its fee structure. Rates increase 37.5 percent this year and about 28 percent a year for the next two years. Moreover, fees are retroactive through the beginning of 2006.

The problem for Internet radio is that many of these small, independent outfits will face bills that will put them out of business. It's a classic case of immediate profit versus long-term gain. For what Internet stations such as Pandora can deliver is a targeted audience that is interested in learning more about specific music. The industry makes a small amount of money from the higher fees while losing the traffic such sites could generate long-term.

Beyond all this, however, is a misconception about what the Internet is doing to traditional media. The Net is not about broadcasting entertainment to a passive audience. It is a communications medium, a place where ideas, images and music move back and forth, following broad arcs of discussion and innovation. Using its strengths can build new audiences.

Does the recording industry really want to stifle market-savvy sites such as Pandora?

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