Lockheed Martin, one of the world's largest defence contractors, is investigating the source of a major cyber-attack one week ago against its information network, the company said.
"Lockheed Martin detected a significant and tenacious attack on its information systems network," the company said in a statement late Saturday night.
The company said the cyber-assault took place on May 21, and that quick action by its security team successfully repelled the attack.
"No customer, program or employee personal data has been compromised," the company statement said, adding that federal authorities had been notified.
"Throughout the ongoing investigation, Lockheed Martin has continued to keep the appropriate US government agencies informed of our actions," the company said.
President Barack Obama has been briefed about the attack, White House spokesman Jay Carney said Sunday.
"It has been part of the briefing materials that he has," Carney said. "My understanding, based on what I've seen, is they feel it's fairly minimal in terms of the damage."
Lockheed Martin said its officials are working "around the clock to restore employee access to the network, while maintaining the highest level of security."
It did not mention the suspected source of the cyber-attack.
The company's information security team detected the attack almost immediately and took what is described as "aggressive actions" to protect all systems and data, the statement added.
The statement said that despite the attack, the company remains confident in the integrity of its "robust, multi-layered information systems security."
Federal officials, for their part, told US media that the consequences of the attack for the Pentagon and other agencies was "minimal," and no adverse effect on their operations was expected.
Headquartered in Bethesda, a Maryland suburb of Washington, Lockheed Martin employs about 126,000 people around the world. It focuses on design, development and manufacturing of advanced technology systems, including some of the military's most advanced weaponry.
Seventy-four per cent of the company's 2009 revenue came from military sales, according to published reports.
Lockheed Martin's products included the Trident missile, P-3 Orion spy plane, F-16 and F-22 Raptor fighter jets and C-130 Hercules military cargo planes among many other major weapons systems.
The company is a primary developer of stealth technology used in U-2 and SR-71 reconnaissance aircraft, the F-117 fighter jet as well as the F-22 and F-35 Joint Strike Fighter designs.
The corporation's 2010 sales from continuing operations reached $45.8 billion (NZ$55.9bn).
However, the stealth Joint Strike Fighter program has faced delays and cost overruns, and the Pentagon overhauled the program last year.
The initial estimate for each F-35 Joint Strike Fighter aircraft was $50 million eight years ago, but more recent estimates were up to $92 million.
Meanwhile, the US space agency Nasa announced last week that a new spacecraft to ferry humans into deep space would be based on designs for the Orion crew exploration vehicle built by Lockheed Martin.
The Orion capsule, originally designed to take astronauts back to the moon, is a surviving component of the Constellation manned space exploration program canceled by Obama last year for being behind schedule and over budget.
The capsule will weigh 23 tons and Nasa has no date set for a potential launch, said Douglas Cooke, associate administrator for Nasa's exploration systems mission directorate.
There is also no final cost associated with the project.
Lockheed Martin is to continue its work on building the space capsule begun in 2006.