Season 5 how Marlo arranges meets and pickups was a good example of extra security.
SPOILER ALERT
Marlo (the drug lord) sent picture messages of a clock to arrange meetings. The hour and minute hands corresponded to the letter and number axes of a common Baltimore map and the second hand tells what page. The dealers would look up the coordinates on a map to find out where to meet. The cops broke it because they had (illegal) wiretaps on everyone's phones, and they had illegally allocated lots of extra manpower to tail all of the suspected drug dealers around the clock.
SPOILER ALERT
Marlo (the drug lord) sent picture messages of a clock to arrange meetings. The hour and minute hands corresponded to the letter and number axes of a common Baltimore map and the second hand tells what page. The dealers would look up the coordinates on a map to find out where to meet. The cops broke it because they had (illegal) wiretaps on everyone's phones, and they had illegally allocated lots of extra manpower to tail all of the suspected drug dealers around the clock.
END SPOILER