Hackers who recently broke into Lockheed Martin's security network used information stolen from the security division of EMC that makes "SecurID" electronic keys, a company official said.
RSA, which makes the keys, said in a letter published on its website that it has confirmed information taken from it in March was used in the attack on Lockheed Martin.
EMC had previously warned that information stolen from RSA related to its SecurIDs.
"Certain characteristics of the attack on RSA indicated that the perpetrator's most likely motive was to obtain an element of security information that could be used to target defense secrets and related (intellectual property)," RSA said in Monday's letter.
RSA will replace the SecurID tokens for any customer who asks, although for most it is probably unnecessary, a company spokesman told Reuters.
Lockheed's networks house sensitive data on future weapons systems as well as military technology currently used in battles in Iraq and Afghanistan.
It was breached through sophisticated attacks that have pierced the defenses of huge corporations including Sony and Google.
The widely used electronic keys work using a two-pronged approach to confirming the identity of the person trying to access a computer system.
They are designed to thwart hackers who might use key-logging viruses to capture passwords by constantly generating new passwords to enter the system.
The SecurID generates new strings of digits on a minute-by-minute basis that the user must enter along with a secret PIN before they can access the network. If the user fails to enter the string before it expires, then access is denied.
