Within the last day, I've seen references to "reverse targeting".
   Apparently it is illegal to use FISA warrants to surveill an American
   citizen, but there is an (also illegal) practice called "reverse
   targeting".  Surveill foreigners that are known to be
   associating/communicating with the desired actual American target, and
   read the resulting NSA 'take'.  This may be what's going on with Trump.

   This is commentary from 2008:
   [1]http://irregulartimes.com/2008/06/24/reverse-targeting-yes-he-can/
     [2]×
   (BUTTON) (BUTTON)
                  Jim Bell

References

   1. http://irregulartimes.com/2008/06/24/reverse-targeting-yes-he-can/
   2. file:///var/lib/mailman/archives/private/cypherpunks/attachments/20170324/3585d393/attachment-tmp.html