Over the past few years, computer attacks, once largely a nuisance issue, have become a threat to national security. Organized criminals have taken advantage of the shift toward online banking and commerce to compromise the financial identity of millions. Even worse, it’s now possible for hackers to cripple government websites during a conflict, or for governments to spy on businesses. Some people even fear that cyber terrorists could use the Internet to damage critical infrastructure such as power stations (see “Moore’s Outlaws”). Concrete numbers on the economic impact of security failures are hard to come by, but the FBI says that losses from cyber crimes in the United States jumped 112 percent from 2008 to 2009.

Cyber attackers exploit fundamental weaknesses in our computer systems (see “The Attacker’s Advantage”). And the threat only grows as more and more businesses around the world become dependent on the Internet, and as more critical infrastructure goes online. To prevent a disaster, experts are working on new defensive technologies, and organizations are even tightening up internal security to protect themselves from malicious insiders. But given that the attackers and their victims are often in different countries, international coöperation will be crucial to improving security, and the necessary agreements have proved hard to reach (see “Global Gridlock on Cyber Crime”).