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ably the truth. There'd been several first-person shooter fans crawling around Valve's Swiss cheese network in anticipation of Half-Life 2. Max happened to be one of them.

The FBI later settled on a different Valve hacker: a twenty-year-old German hacker named Axel “Ago” Gembe, who admitted to his intrusions in e-mails to Valve's CEO, though he too denied stealing the code.

Gembe was already notorious for creating Agobot, a pioneering computer worm that did more than just spread from one Windows machine to another. When Agobot took over a machine, the user might not notice anything but a sudden sluggishness in performance. But deep in the PC's subconscious, it was joining a hacker's private army. The malware was programmed to automatically log in to a preselected IRC room, announce itself, and then linger to accept commands broadcast by its master in the chat channel.

Thousands of computers would report at once, forming a kind of hive mind called a botnet. With one line of text, a hacker could activate keystroke loggers on all the machines to capture passwords and credit card numbers. He could instruct the computers to open secret e-mail proxies to launder spam. Worst of all, he could direct all those PCs to simultaneously flood a targeted website with traffic—a distributed denial-of-service attack that could take down a top site for hours while network administrators blocked each IP address one at a time.

DDoS attacks started as a way for quarreling hackers to knock each other out of IRC. Then one day in February 2000, a fifteen-year-old Canadian named Michael “MafiaBoy” Calce experimentally programmed his botnet to hose down the highest-traffic websites he could find. CNN, Yahoo!, Amazon, eBay, Dell, and E-Trade all buckled under the deluge, leading to national headlines and an emergency meeting of security experts at the White House. Since then, DDoS attacks had grown to become one of the Internet's most monstrous problems.

Bots like Ago's marked the decade's major innovation in malware, inaugurating an era where any pissed-off script kiddie can take down part