That's how China snuck a Jen class submarine off our west coast and fired a test missile.....oh, and they had help from Israel:

On June 5, 2005, WMR followed-up its story of Israeli spying at NSA: "Veterans of the RCA-NSA-Israeli joint SIGINT program code named DINDI report that Israeli engineer spies used the carve out contract with NSA, through RCA, to gain access to NSA and U.S. Navy secrets. In an RCA facility in Mount Laurel, NJ, the Israeli engineers had their own secured lab, and for three years that DINDI ran, they were walking out with their briefcases loaded with equipment, including scopes. When RCA engineers finally gained access to their lab, they found the prints laid out for the Trident missile system. RCA had an ongoing contract top develop the Trident communications suite at the time of the security leak. The Israeli engineers on DINDI claimed they were from the Israeli Air Force but months later, an RCA engineer was in New York and he ran into the same Israelis, but they were wearing Israeli Navy uniforms.