Unknown hackers have broken into the security networks of Lockheed Martin Corp and several other U.S. contractors, a source with direct knowledge of the attacks told Reuters.
The breach occurred when hackers created duplicates to SecurID electronic keys from EMC Corp's RSA security division, a person not authorized to publicly disclose the matter said in the report.
It was not immediately clear what data, if any was stolen.
Hackers learned how to copy security keys with data stolen from RSA during an attack EMC disclosed in March, the source told Reuters.
The agency also contacted General Dynamics, Boeing, Northrop Grumman, Raytheon and other defense companies who declined to comment.
In March, EMC admitted that its security division RSA became a victim of an advanced cyber attack.
EMC said measures instituted to protect the RSA and its customers included hardening our IT infrastructure. The company has begun an investigation and is working with authorities, he said.
The attack type is known as an Advanced Persistent Threat(APT)
Customers were informed of the breach and were being provided ways to strengthen the product's implementation