A total of 215,092 members of the Gülenist Terror Group (FETÖ) are said to have used ByLock, a messaging app, for secure encrypted communication, confirmed the indictment prepared by the Istanbul Chief Public Prosecutor's Office. It was further stated in the indictment that 184,298 of the total ByLock users were revealed by intelligence forces. The prosecutors said ByLock was popular among FETÖ members between 2013 and 2015. After 2015, the terror cult turned to Eagle IM, which offers "256-bit end-to-end AES encryption," according to the app's description on its Google Play Store page.

It also revealed that the group's leader, Fetullah Gülen, used to send out instructions through the ByLock messaging app.

"All members must make calls through ByLock, those who use regular phone communication, would betray the mission," Gülen reportedly told FETÖ members, the indictment stated.

Bylock users, who worked in the civil services and as bureaucrats are now being investigated for their possible links to FETÖ. Several suspects linked to the terror group have already confessed to using ByLock.

The indictment emphasized on ByLock's importance and FETÖ's reliance on the app, which is not possible to install without a setup file that is not available on the internet. Thus the only way to reach the setup file was to get it from another member. This also helped FETÖ to keep tags on authorized members.

The prosecutor's office said ByLock's servers were hosted in Lithuania and a message sent through the app would automatically be deleted by the system within 24 hours.

In addition, it was mentioned that the screenshot and copies of the incoming messages could be taken in accordance with the characteristics of the phones. ByLock was first offered in English and later rolled out a Turkish language update to help provide accessibility to FETÖ members in Turkey. After the update, the app was called as "Turquoise."

Before the Gülenist failed coup attempt in July 15, 2016, ByLock was removed from Google Play Store as well as Apple's store, however, its services were open for access.

Meanwhile, Turkish police on Saturday arrested 132 people, including police officers, as part of an investigation into FETÖ.

Security forces raided some 325 locations in 49 provinces across the country in the operation that targeted 235 suspects, including 187 police officers.

Meanwhile, detention requests for 180 members of the Turkish Armed Forces were issued, in an operation related to the ByLock probe in 48 provinces throughout the country.