Iran, it turns out, has not only been smuggling in materials and technology for their weapons industries, but is also recruiting people with specialist skills. This is particularly the case with their nuclear weapons program. Now you'd think that Iran, with such a highly educated population, and so many graduates in science and engineering, would have no problem getting the skilled people they needed locally. Such is not the case. There is no love lost between the educated Iranians and the Islamic dictatorship that has run the country for the last three decades. The disdain is mutual, as the Iranian technocrats have always been mistrusted by the clergy (whose core supporters are poorly educated country folk.) Highly educated Iranians prefer to flee the country. This brain-drain has left the clerical leadership with a techie shortage. So they have had their agents scouring the world looking for mercenary technocrats, willing to think, and produce better weapons for a good payday.
One of the best sources has been North Korea, which has made renting their labor force to foreigners into a major source of foreign exchange. The collapse of the Soviet Union in 1991 left thousands of good Russian weapons techs jobless. Some converted to commercial work, but many eventually decided they would travel if the pay was right.