Other U.S. officials did confirm to NBC News that the drone had flown previous missions over Iran.
Did Russia send Iran a digital drone killer?
It's not clear whether Iran actually did bring the drone down, let alone whether it was downed by anti-aircraft missiles or guns, or if it was brought down with electronic countermeasures (ECM).
ECM systems are normally carried on fighter planes to scramble radar, GPS and other anti-aircraft gun or missile guidance systems. Used from the ground against drones, ECM can break the link with pilots flying with remote control or confuse the guidance systems within drones programmed to fly on their own using GPS or other internal guidance systems.
Iran claimed in July to have shot down an American drone, but admitted later the report was part of a defensive war-games exercise, not a real incident.
Six weeks ago Russia announced it sent Iran an electronic jamming system called "Avtobaza", which might have been able to interfere with the guidance systems and electronics on the RQ-170, according to sources quoted in Wired.
RQ-170s are programmed with two levels of safety systems; the first, which takes over if the drone loses radio-control contact with controllers, tells it to use onboard GPS and navigational equipment to fly back to the base from which it took off.
The second, though unconfirmed, safety system is a self-destruct system that would ruin the full-motion capture, encryption and radio-control systems that would give Iranian engineers – or more likely engineers from allies Russia or China – insight into operation and security of America's newest front-line drone, according to National Journal.