El Chapo's Opsec
El chapo then switched to a complex system of using BBM (Blackberry’s Instant Messaging) and Proxies. The way it worked was if you needed to contact The Boss, you would send a BBM text to an intermediary (who would spend his days at a public place with Wi-Fi) this intermediary (or “mirror”) would then transcribe the text to an I-Pad and then send that over a Wi-Fi network (not cellular networks which were monitored constantly by law enforcement). This WiFi text was then sent to another cut-out who would finally transcribe the message into a Blackberry BBM text and transmit it to Guzman. Although Guzman continued to use his Blackberry, it was almost impossible to analyze the traffic because it now only communicated with one other device. This “mirror” system is difficult to crack because the intermediaries or proxies, can constantly change their location by moving to new WiFi spots.
This article claims he was caught because of a large food order:
After construction was complete, the safehouse was quiet. Until 7 January 2016, when a car arrives carrying unknown passengers. Security forces suspected that this was Guzman. There was one final indicator that someone important enough to require an entourage was inside. A white van went off, at midnight, to fetch enough tacos to feed a large group of people. The police raided the house 4 hours later.
Here’s more detail about El Chapo’s opsec at the time of his previous capture.