This form of surveillance would be a game of bingo: for a given "bad" domain you have multiple individual URLs that a browser would hit. Put a few of them on th

This form of surveillance would be a game of bingo: for a given "bad" domain you have multiple individual URLs that a browser would hit. Put a few of them on the trigger watchlist, grouped by domain, and when a browser hits some threshold number of the same group within seconds the algorithm shouts "bingo" because chances are this won't be unrelated collisions. Note also that mass surveillance isn't partucularly concerned about false positives.