was that el chapo's people kept changing what are called burner phones, disposable phones used a short time and then tossed away. >> don't you have to go back to square one every time they toss them? >> if they drop their phones all at the same time, yes. but there's -- there's hundreds of people in this organization. and they're not all dropping their phones at the same time. >> i toss my phone now. she tosses her phone tomorrow. you're three days later. that was their weakness? >> right. >> it's not registered in anyone's name, how were you able to identify where these communications were coming from? >> through the names that they were using. they were very open in their communications. >> it was a big mistake by el chapo's operation. drew and the team could now track them, and the cartel operatives had no idea. >> they didn't think that those communications could be intercepted by u.s. law enforcement. >> were you actually reading their texts? >> every single one of 'em. >> could you tell where they were coming from and whether you were in fact seeing