The U.S. Defense Department must secure the cyber domain to protect and defend its own information and U.S. citizens, Gen. Keith B. Alexander, USA, commander of U.S. Cyber Command said today during the opening address of LandWarNet 2010. Gen. Alexander also serves as the director of the National Security Agency. "Every link and system has vulnerabilities that we have to defend," he stated. Gen. Alexander organized his speech by comparing warfare in the past with the movie WarGames and cyberwarfare to the movie The Matrix. In the former movie, as in nuclear warfare, there is no good engagement option because of assured mutual destruction.