The latest version of Conficker isn't the first bot to plague the Internet, but it may be the smartest and most sophisticated. And it starts phoning home Wednesday.

But whoever they are, they sure are dangerous. "We must also acknowledge the multiple skill sets that are revealed within the evolving design and implementation of Conficker," wrote security experts at the research group SRI International in a report last week. The researchers added: "Perhaps an even greater threat than what they have done so far, is what they have learned and what they will build next."

But Conficker is also important for what it portends about the inherent difficulties of living in a networked age. Worms feed on bugs—holes in the ever-more-complex operating systems and Web browsers where we live most of our online lives. And because we're never going to get rid of these bugs, bad guys will always be able to find a way in. It's just that now, with the entire Internet as their playground—and with the power to harness all their infected machines into a thinking network—they can cause tremendous harm. Conficker could fizzle. But you can bet that someday, something very much like it will cause a lot of pain.