Although interception due to screening or random chance is likely the most common reason for a customer to be arrested, we must keep in mind that we may not know the cause of an interception. It is entirely possible that some interceptions that appear to be due to screening or random chance are actually due to technical attacks or even more likely human intelligence. I have seen cases where multiple large shipments to different people were sent out at the same time, and all of them were intercepted. There are many possibilities of how this could have happened. It could be that they were randomly screened for contraband, it is possible that they were flagged, it is possible that one of them was intercepted and the others were identified due to sequential tracking numbers, it is possible that the one that was flagged was flagged because tracking was checked with Tor, it is possible that an undercover compromised the shipper, etc etc. In a case where a technical attack leads to an interception, it is entirely possible that the technical attack that leads to the intelligence will never be revealed in court even. There is a big distinction between intelligence and evidence, intelligence points the agents to where they must look for evidence. Evidence in a drug case will always be in the form of the intercepted drugs, but the intelligence that leads to the interception taking place could be from a wide variety of different things, and it may never be revealed. It is similar to when people are 'randomly' pulled over and subjected to a drug search. In some cases they may have committed a minor traffic violation and been pulled over for that, in some cases they may have acted in a suspicious way and been flagged for that. Indeed, in the majority of cases somebody arrested for transporting drugs via a vehicle will probably have originally been pulled over for unrelated traffic violations or for having been behaviorally flagged. However, in many of the cases they will have already been identified as having drugs due to human intelligence, or due to technical intelligence, but this will not be revealed if the conviction can be obtained based upon the evidence obtained during a 'routine' traffic stop.