Fifteen people were detained Thursday in the Aksaray province of central Turkey due to their usage of the encrypted communication application Bylock, as part of the Gülenist Terror Group (FETÖ) investigation carried out by the Aksaray Public Prosecution Office.

It was revealed that the suspects, who are also professional schoolteachers, were Bylock users, an app that is known to be used by members of FETÖ for internal communication.

Meanwhile, 18 people were detained yesterday in the western province of Çanakkale as part of the ongoing investigation as well. They also have been detained due to their usage of Bylock.

FETÖ members use this application on their smartphones to share information and communicate with each other.

There is another messaging application used by FETÖ members called Eagle. Some 50,000 members use the Bylock and Eagle system.

Testimony from Gülenists in the bureaucracy detained after the July 15 putsch attempt pointed to the prevalence of the use of apps. Prosecutors say Bylock was popular among Gülenists for secretive communications between 2013 and 2015, and after 2015, the terror cult turned to Eagle IM, which offers "256-bit end-to-end AES encryption" for its users, according to the description of the app in the Google Play Store. The app's developers also promise protection from "Man In The Middle" attacks or hacking into chats between two people that enables message altering by one of the two parties. Similarly, Bylock was offering an eight-digit password for users and highly secure encryption.