Lockheed Martin hit with 'significant and tenacious' cyber attack

The world's largest defense contractor said Saturday it fought off a "tenacious" cyber attack last week.

Lockheed Martin Corp, the Pentagon's No. 1 supplier, said in a statement it detected a "significant" assault on its computer networks on May 21. It was found "almost immediately" and no employee, program or customer data was lost, the company said in a statement.

The Department of Homeland Security said it knew about the "cyber incident," and was investigating alongside the Department of Defense.

The agencies are "determining the extent of the incident, performing analysis of available data in order to provide recommendations to mitigate further risk," said Chris Ortman, a spokesman for the agency.

Lockheed uses a mobile security system produced by EMC Corp.’s RSA unit. RSA bolstered security for clients, including Lockheed, after a network breach in March resulted in the theft of RSA data, a person familiar with the process said.

Weapons makers are the latest companies to be breached through sophisticated attacks that have pierced the defenses of huge corporations including Sony and Google.