THIS ACHIEVEMENT IS BEST PURSUED AFTER YOU GET ELECTROCUTIONER'S SHOCK GLOVES!!!!
As you progress through the game, the Enigma Side Mission will unlock. Afterwards, you will discover Enigma Data Handlers scattered around the map. Set a custom marker on one of their locations, beat him and any other thugs up, and then interrogate him after the fight. He will reveal where some of the Extortion Files in the district are. Repeat this process in one district (E.g. The Bowery) until all Extortion Files are revealed. Each district has two sets of Files marked on the map as a part of Set#3, Set#7, etc. (The Bowery has sets 3 and 4 I think). Set a custom marker on your map to find each file and complete the set. BOOM, 10 GAMERSCORE ADDED TO YOUR ACCOUNT!!!!