''Protecting airmen's personnel information is something we take very seriously," Major General Tony Przybyslawski, commander of the personnel center, said in a statement. ''We are doing everything we can to catch and prosecute those responsible."
The Social Security numbers, birth dates, and other information were accessed sometime in May or June, apparently by someone with the password to the Air Force computer system, Brabenec said.
On Friday, the affected people were told how they can protect their identity, he said.
The military, while protecting classified information, has had trouble protecting data about its people, a computer specialist told the Washington Post, which first reported the story.
''They have historically done much better at protecting operational systems than at protecting administrative systems," said John E. Pike, director of GlobalSecurity.org.
Hacking has been on the rise in commercial industry.
In July, business leaders announced an education campaign to better protect sensitive client information from hackers and other thieves.
In June, CardSystems Solutions Inc. disclosed that a breach of its system that processes transactions between merchants and credit card issuers exposed 40 million accounts to possible fraud.
