Privately-owned U.S. computer networks remain vulnerable to cyber attacks, and many U.S. companies are not doing enough to protect them.

"I hope this isn't one of those situations where we won't do what we need to do until we get slammed," Deputy U.S. Defense Secretary Ashton Carter said in a Reuters report.

In the report, Carter said the Pentagon was doing all it could to protect its own networks and develop offensive cyber weapons, but shoring up the nation's overall cyber infrastructure —  much of which is privately held — was far more challenging.

"When it comes to the nation's networks there are many other forces and considerations that make it very complicated, and therefore very slow, and I'm concerned that it's moving too slowly," he told Reuters after his remarks at the conference.

"We're still vulnerable and the pace is not adequate," Carter said in the report.