WHEN I FIRST MET BARRETT LYON in 2004, I was covering Internet security for the Los Angeles Times from an office in San Francisco. His story was so good—and met a journalistic need so deep—that I had a hard time believing it was true.

For more than a year, I had been grappling with an onslaught of urgent but complicated stories. Seemingly every week brought a new computer virus that shot around the world. Many had real impact, shutting down large company networks or overstuffing mailboxes with spam until they started rejecting legitimate messages. Even so, the problems could be hard to explain before the deadline for the next day’s newspaper—especially if the viruses took advantage of obscure software holes in ways experts were still struggling to understand.

It wasn’t just that the technical explications were tricky. There were few heroes, except for a handful of almost unquotably nerdy researchers. The villains were usually shadows. When someone did get caught in those days, it was typically a maladjusted teenager.

In this disquieting cyber thriller, Joseph Menn takes readers into the murky hacker underground, traveling the globe from San Francisco to Costa Rica and London to Russia. His guides are California surfer and computer whiz Barrett Lyon and a fearless British high-tech agent. Through these heroes, Menn shows the evolution of cyber-crime from small-time thieving to sophisticated, organized gangs, who began by attacking corporate websites but increasingly steal financial data from consumers and defense secrets from governments. Using unprecedented access to Mob businesses and Russian officials, the book reveals how top criminals earned protection from the Russian government.

Fatal System Error penetrates both the Russian cyber-mob and La Cosa Nostra as the two fight over the Internet’s massive spoils. The cloak-and-dagger adventure shows why cyber-crime is much worse than you thought and why the Internet might not survive.