Also immigrants or visitors who were entrusted with nuclear secrets: Klaus Fuchs, who sold Manhattan Project secrets to the Soviets; Harry Gold, who helped Fuchs; George Koval, born in the U.S. but raised in the Soviet Union and trained there as a spy, who successfully penetrated the Manhattan Project and passed details about its nuclear technologies to the Soviets; Allan Nunn May, who obtained U.S. secrets while visiting from Canada and sent them to the Soviet Union; Wen Ho Lee, probable case of passing nuclear secrets to China, but convicted only of mishandling data. Those are just the ones who were caught. Most leakers don't get caught.