The system—used for simulating weapons tests—was not supposed to be connected to Internet. The Institute is located in Sarov, a "closed" city east of Moscow where nuclear weapons research has been conducted since 1946. The facility is so secret that it was left off Soviet maps; Sarov is surrounded by fences and guarded by the Russian military accordingly. While the city is the home of Russia's Nuclear Weapons Museum, don't plan a visit anytime soon—access to Sarov is restricted, and no one who does not live in the city is allowed to visit without permission. Foreigners visiting on official business...