operatives. this material would be used for what they call a dirty bomb. this is when you take loose nukes, loose nuclear material, you fashion it around an explosive device and it exploeds, contaminating entire city weeks so it effectively shuts down large areas of urban areas. this is, believe me, the crown jewel for groups like al qaeda and now it seems isis as well. >> you say there are four attempts. i always think there's so many things that we often do miss. we miss when pakistan tested a nuclear weapon. is there any suspicion there were successful sales? >> based on some independent reporting we've done here at fox news, it certainly suggests that this is just the tip of the iceberg, that there were other incidents as well. there was one case in particular where they caught it very far down the pike in the sting operation and they were lucky to kind of intervene and disrupt it. the key thing that the