Cybersecurity is an elusive goal: Breaches such as the theft of more than 4 million sensitive records from the U.S. Office of Personnel Management make news, but countless others go unreported. Security experts warn that many countries around the world are now engaged in a high-stakes digital arms race both to boost protection and to create offensive tools. But unlike the nuclear arms race, cyberweapons are much easier to come by: Cash and computers are the essential prerequisites. We discuss the threat of cyberattacks and what governments and businesses are doing to block them.