CNet is running a piece looking at what they refer to as a 'questionably legal' internet surveillance technique being employed by the FBI. In situations where isolating a specific IP address for a suspect is not possible, the FBI has taken to 'full-pipe' surveillance: all
activity for a bank of IPs is recorded, and then data mining is used to attempt to isolate their target
. The questionable legality of this situation results from a requirement that, under federal law, the FBI is required to use 'minimization'. The article describes it this way: "Federal law says that agents must 'minimize the interception of communications not otherwise subject to interception' and keep the supervising judge informed of what's happening. Minimization is designed to provide at least a modicum of privacy by limiting police eavesdropping on innocuous conversations."
Full-pipe surveillance would seem to abandon that principle in favor of getting to the target faster.