In these cases, there is little chance that the subject would be able to find out about the surveillance. Government use of electronic surveillance is governed by several laws. Because of traditional difficulties with the U.S. Postal Service, some problems with mail delivery will occur, such as a machine catching an end of an envelope and tearing it, or a bag getting lost and delaying delivery. Remember that the glue on envelopes doesn't work as well when volume or bulk mailings are involved. Mail may never arrive.
More leeway is given for opening first class international mail.
Bureau agents were given special training in burglary, key reproduction, etc. for use in entering homes and offices. Items of obvious financial value are left untouched. Signs of a political motive are left, such as putting a membership list or a poster from an important event in an obvious place. Informers and Infiltrators Information about an organization or individual can also be obtained by placing an informer or infiltrator. Once someone joins an organization for the purposes of gathering information, the line between data gathering and participation blurs.