In Iran, the US uses electronic surveillance of Iranian officials. The CIA monitors so called 'Geo-spatial Intelligence' and radar imagery. Some analysts believe drones prowl Iranian territory for undisclosed nuclear evidence. There are clandestine ground sensors to detect radioactive signatures. All this information is shared with Israeli National Security officials. But collecting independent human intelligence... to verify a nuclear weapons program, is an uncertain science in the best of circumstances. According to the US Security officials, Tehran has not crossed the 'nuclear weaponization' red line. But for obvious reasons, the Israelis have a more stringent analysis. It's not something they can be wrong about... their national security is at stake.
Man shot dead in northern Israel town of Bi'ina, police say the murder was gang related (Haaretz)
from the article: 'Mossad, CIA agree Iran has yet to decide to build nuclear weapon'