Don't Be Dragooned Into the Botnet Army

A favorite multipurpose weapon of online thieves is growing larger and more powerful, according to those who combat the threat.

The malware armies are growing, with a sharp rise in the number of computers corralled into botnets--far-flung networks of infected PCs that digital crooks use to steal financial account data, relay spam, and launch crippling Internet attacks. Now that popular Web sites can invisibly and unwillingly spread malicious software, the days of staying safe just by being careful where you surf are sadly long gone. But you can take steps to protect yourself and your PC from these threats.