my theory is anyone who stays in US (gc/h1/f1/citizen) visiting certain countries of interest get tagged in some database and thereafter a passive record is maintained esp of financial dealings like large money transfers in or out, frequent visits, phone calls to certain countries....and some mapping sw also builds webs of links between such people for the database. filters and rules are installed to red flag someone whose activity profile hits a rule like say "visits pakistan twice in six months, gets $100k via western union from sudan and spends hangtime at the local islamic center owned by a cleric with known feelings"
in the interest of not attracting civil rights lawsuits or congressional criticism during political fractures, they probably tack on a whole lot of other innocents into the mix - like people of india, slovak republic, argentina and taiwan - just to keep it 'fair n balanced' and 'fully 200% secular'.
a nice black ops name like Project Arachnid or ThoughtMatrix with deputy directors of CIA, FBI and homeland security jointly chairing the board.
some electronic spider somewhere is logging all your hours on BR for sure
trust no one Mr Anderson.