As threats of a crippling cyberattack against the United States have mounted, the Obama administration has pushed repeatedly for stronger digital defenses while remaining quiet about its own hacking arsenal.
But in a rare public disclosure this week, a top general acknowledged that the United States is focused not only on playing defense on the cyber battlefield -- it is also bolstering its offense.
Gen. Keith Alexander, who runs the Pentagon's Cyber Command, told Congress on Tuesday that he is establishing 13 teams of experts to carry out cyberattacks against foreign countries that target the United States with destructive computer code.
“I would like to be clear that this team, this defend-the-nation team, is not a defensive team,” Alexander told the House Armed Services Committee. “This is an offensive team that the Defense Department would use to defend the nation if it were attacked in cyberspace."
While Alexander made his comments to Congress, several experts interpreted his remarks to be directed abroad, serving as a veiled threat to foreign adversaries that could persuade them to negotiate a cyber arms treaty with the United States.
James Lewis, a senior fellow and director of technology policy at the Center for Strategic and International Studies, said he hopes Alexander's remarks will convince other countries to be more forthcoming about their hacking skills.
"Russia and China have powerful cyber capabilities, but they won't talk about them," Lewis said. "That's what worries me."
Alexander's comments came one day after a White House official demanded that the Chinese government, which has been accused of sponsoring cyberespionage against American companies, agree to “acceptable norms of behavior in cyberspace." But Lewis noted that China is not the only country to worry about -- about a dozen countries have the capacity to launch cyberattacks against the U.S., he said.
Alan Paller, director of research at the SANS Institute, a nonprofit security research and education organization, echoed Lewis' hope that other countries may now be persuaded to disclose their cyberweaponry. He added that Alexander's comments may help pave the way for a potential cyber arms treaty.
"When we wanted to have nuclear arms treaties, we had to share our capabilities," Paller said. "You can't have an arms treaty if you don’t know what the other guys have. This may be the first step."
Col. Rivers Johnson, spokesman for the Pentagon's Cyber Command, did not return a request for comment about the general's comments.
Alexander's remarks coincided with those of James R. Clapper Jr., the nation’s top intelligence official, who warned Congress on Tuesday that a potential cyberattack that cripples the country's power grids, communications networks and financial systems poses a greater threat to the United States than global terrorist cells.
The United States has carried out one known cyberattack against another country, when President Barack Obama secretly ordered an attack that damaged Iran's nuclear facility. U.S. officials have never publicly acknowledged their role in the attack, known as Stuxnet, and have said little about America's offensive cyber muscle ever since.
But last summer, the Air Force made a rare public call for contractors to develop "cyberspace warfare attack" capabilities. And last month, The New York Times reported that a secret legal review concluded that Obama has the power to order a pre-emptive cyberattack if the United States has evidence that another country has targeted it with destructive computer code.
Now, the U.S. military is creating teams of hackers to carry out those pre-emptive cyberattacks. And by disclosing that publicly, Alexander may deter foreign adversaries from launching attacks in the first place, said Roger Cressey, a former White House cybersecurity and counterterrorism official.
"When you talk about it publicly, there is an element of deterrence," he said. "It's putting other countries on notice that a potential cyberattack will be responded to."