Lockheed Martin, the Department of Homeland Security and the Pentagon confirmed that the contractor’s information systems had come under attack. Lt. Col. April Cunningham, speaking for the Defense Department, said the impact on the Pentagon "is minimal and we don’t expect any adverse effect."

Still, the concerted attempt to breach the contractor’s systems underscored the risk to the nation’s critical defense data. Chris Ortman, Homeland Security spokesman, said his agency and the Pentagon were working with the company to determine the breadth of the attack and "provide recommendations to mitigate further risk."

Lockheed Martin said in a statement that it detected the May 21 attack "almost immediately" and took countermeasures. As a result, "our systems remain secure; no customer, program or employee personal data has been compromised." The company’s security team is still working to restore employee access to the targeted network. Neither Lockheed Martin nor the federal agencies revealed specifics of the attack.

___

AP writer Jennifer Malloy contributed to this report from Los Angeles.