WASHINGTON (Reuters) - The Pentagon's No. 1 supplier, Lockheed Martin Corp, on Monday cited dramatic growth in the number and sophistication of international cyber attacks on its networks and said it was contacting suppliers to help them shore up their security.Chandra McMahon, Lockheed vice president and chief information security officer, said about 20 percent of the threats directed at Lockheed networks were considered "advanced persistent threats," prolonged and targeted attacks by a nation state or other group trying to steal data or harm operations."The number of campaigns has increased dramatically over the last several years," McMahon