Soon the two countries had developed a complex worm that the Americans called the bug. But the bug needed to be tested. So, under enormous secrecy, the United States began building replicas of Irans P-1 centrifuges, an aging, unreliable design that Iran purchased from Abdul Qadeer Khan, the Pakistani nuclear chief who had begun selling fuel-making technology on the black market. Fortunately for the United States, it already owned some P-1s, thanks to the Libyan dictator, Col. Muammar el-Qaddafi.
When Colonel Qaddafi gave up his nuclear weapons program in 2003, he turned over the centrifuges he had bought from the Pakistani nuclear ring, and they were placed in storage at a weapons laboratory in Tennessee.