A Jordanian border official said at a news conference Wednesday that Islamic State militants are using homing pigeons to deliver messages to operatives outside its so-called caliphate.

Brig. Gen. Saber al-Mahayreh said Jordanian troops captured one of the pigeons sent by ISIS fightes in Iraq to a person in Jordan with a letter addressed to him. Al-Mahayreh said militants are using outdated ways to get its messages out, aside from using social media.

“The jihadists tied a letter with a phone number to the foot of the bird, which was flying to a Jordanian resident,” he said.

ISIS leaders have encouraged followers to use encrypted apps such as What’s App and Telegram in the past to get around Western security.

According to The Telegraph, counterterrorism groups believe the extremists have developed their own encrypted app the hides their digital communications.

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