Air Force Chief of Staff Gen. Norton Schwartz told a House hearing last week that U.S. government unclassified computer networks are experiencing an attack a second.

Cyber strikes are “a major issue on our unclassified networks,” Schwartz told the House Appropriations subcommittee on defense.

“I've been speaking for 15 seconds. We probably had 15 attempts to work into the system,” he said. “We are reasonably secure, but on the classified side, I would indicate that we are quite secure, very secure."

The attackers are varied and include foreign governments, individual hackers and criminal networks as well as “fun-seekers,” he said.

Schwartz also said there are foreign counterintelligence concerns related to attacks on BlackBerrys and other handheld devices.

“It's a counterintelligence concern and one that we take seriously,” he said.

U.S. counterintelligence officials have said China’s intelligence services pose a serious threat to all handheld devices that enter Chinese wireless communications space. In one case, a security professional discovered a government listening device that had been covertly planted on a cellular device between the time he arrived at the airport to the time he reached his Beijing hotel.