The chairman of the U.S. Joint Chiefs of Staff has called for increased protection of U.S. information networks from cyber attacks.

While addressing the National Press Club in Washington Thursday, Navy Admiral Mike Mullen said he has become increasingly concerned about a recent wave of cyber attacks targeting U.S. and South Korean Web sites.

He said that leadership across the board, as well as information experts, recognize and are addressing the threat.

But Mullen did not elaborate on the culprit behind the cyber attacks, saying only that the Defense Department is in the midst of a thorough probe.