Hackers launched a "significant and tenacious" cyber attack on US defence contractor Lockheed Martin, which holds highly sensitive information, but its secrets remained safe, the company said today.
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 Defence 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 defence 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 it detected the May 21 attack "almost immediately" and took counter-measures. As a result, "our systems remain secure; no customer, programme 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 government agencies revealed specifics of the attack.