In jail, corrections officers are constantly monitoring the mail inmates send and receive.
They’re looking for any number of things hidden in the envelopes – drugs, money, or contraband items like cell phones, for example.
But in many cases, they’re looking for something much harder to spot: secret codes.
That was the case last year at Fulton County Jail in Atlanta, when staff intercepted a letter from an inmate that looked innocuous, but actually contained an encoded message ordering a hit on a staff member.
Cracking codes is the specialty of the FBI’s Cryptanalysis and Racketeering Records Unit, which details on itswebsite the various types of secret codes, or ciphers, used by inmates.
We’ve compiled some of the most commonly used codes below:
Source: Business Insider (Mark Abadi)
Photo Credit: Col. Mark Adger/Business Insider/Mark Abadi
Photo Credit: fbi.gov
Photo Credit: YouTube/CodeBreakers
Photo Credit: Center for Health Journalism
Photo Credit: Mail | Middlesex Sheriff