Lockheed Martin has acknowledged the "persistence" to attack computer networks this month, but said that no customer information was compromised.
The company issued a statement saying he was told on Saturday of a "significant and persistent attack" on May 21 said the security team of the company information to quickly detect the attack and that no customer, program or data staff has been compromised.
He did not elaborate on the nature of the attack.
"During the investigation, Lockheed Martin continued to maintain the appropriate U.S. government agencies for information on our activities," the statement said. "The team will continue to work all day to restore the employee to have access to the network, while maintaining the highest level of security."
Lockheed Martin is one of the world's largest aerospace companies. It is approximately 126 000 workers, according to the statement.