Defence giant Lockheed Martin has confirmed that its IT infrastructure was targeted by cyber criminals last week.
It described the attack on its information systems, which occurred last Wednesday, as being "significant and tenacious".
Lockheed Martin said that the company's information security team detected the attack before any harm was done.
Consequently no customer, program or employee data was compromised, it said.
Lockheed Martin informed US government agencies of the attack as soon as it was discovered.
Lockheed Martin, which employs about 126,000 people worldwide, researches, designs, develops and manufactures advanced technology systems, products and services.
This is the latest in a series of high-profile cyber attacks, with Amazon and Sony also recently falling victim.
Ross Brewer, vice president and managing director of international markets at security and compliance specialist LogRhythm, explained how companies such as these can trace the cyber criminals.
"Critical clues to how the attack was launched and spread will be held in the log data generated by every device and application on Lockheed Martin's network. By analysing these logs, the company should be able to spot patterns of suspicious behaviour and work backwards to pinpoint the cause," he said.