blast and building and detona detonating bombs like testing recipes in a cookbook. >> we went out and looked what was available on the internet and what was being published by organizations that want to be nefarious things in the united states. >> reporter: like "inspire" magazine? >> right. >> reporter: that is the al qaeda publication in which the tsarnaev brothers found the pressure cooker bombs detonated at the boston marathon. >> reporter: we can look at investigative leads that occurred like where would they have gotten materials or supplies and helps an variation follow up. >> reporter: agents say what may be the greatest advancement of the last 20 years, the cell phone. think back to 19931995. it was basic. now agents it take photos and shoot video and e-mail them back