Lockheed Martin, the United States government's top information technology provider, says there has been a significant attack on its information systems network, but that it has been thwarted.
It says no customer, program or employee personal data has been compromised.
Lockheed Martin spokesperson, Jennifer Whitlow, said in an emailed statement that the company was working around the clock to restore employee access to the targeted network while maintaining the highest security level.
She said it has kept US government agencies informed of its actions.
The US Defense Department says it has been working with Lockheed to determine the scope of the attack, which occurred last week.
Lockheed is the world's biggest aerospace company and the Pentagon's number one supplier by sales.
It makes fighter jets, ships and other multibillion-dollar arms systems sold worldwide.
