Amid the debate over privacy concerns, several people are switching to Telgram and Signal from WhatsApp, but the terrorists in India and abroad are using a much more advanced secure messaging platform to communicate with their counterparts across the globe without being traced and without leaving any digital footprint, a National Investigation Agency (NIA) probe has revealed.

The NIA during its probe into the Islamic State Iraq and Syria Khorasan Province (ISIS-KP) case has found that arrested accused Jahanzaib Sami Wani and his wife Hina Bashir Beigh and Bengaluru-based doctor Abdur Rahman aka 'Dr Brave' were using Threema, a secure messaging platform.

Wani and Beigh were arrested in March 2020, while Rahman in August.

In a statement on January 12, an NIA spokesperson had said: "Till recently Rahman was in regular communication with ISIS terrorists located abroad as well as in India, including Sami on 'Threema', a secure messaging platform."

The revelations were made on Tuesday when the anti-terror-probe agency filed a chargesheet against Rahman, who had returned from Syria in December 2013 and was misusing his medical knowledge to develop laser-guided missile system for the banned terror group.

According to NIA officials related to probe, who wished ro remain anonymous, said that Rahman was using his knowledge of ophthalmic lasers for developing a project on laser-guided system through which the trajectory of an unguided missiles can be changed with laser technology for the benefit of ISIS.

The official said that the "basic components" for such system are pulse transmitters and receivers, which are same or almost similar in flight circuits or ophthalmology nanosecond lasers and could be used to guide missiles or rockets or payloads towards intended targets..

The NIA ISKP case is based on the one registered by Delhi Police's Special Cell in March 2020 after the arrest of Wani and his wife from Okhla Vihar in Jamia Nagar area here for alleged links with the the terror group.

The NIA had taken over the probe on March 20, 2020.

However, this is not the first time that the NIA has come across the secure messaging platform used by the IS terrorists as well as Hizbul Mujahideen, Lashkar-e-Toiba and Al Qaeda terrorists.

Earlier, the NIA has taken the help of the Federal Bureau of Investigation (FBI) to crack the messages of the terrorists in connection with its probe into the February 2019 Pulawama terror attack case, in which 40 CRPF troopers were killed.

The NIA and the Intelligence Agencies in its probe had earlier found that Jaish-e-Mohammad terrorist were using peer-to-peer software service -- YSMS -- or a similar mobile application to communicate with their counterparts in India and abroad.

An NIA source related to probe told IANS: "The terrorists are using Threema application as well as its desktop version as it leaves minimal digital footprint making it almost impossible to be traced back.

"Tracing of the message or call generated from the Threema are tough to locate."

According to NIA officials, Threema is a secure messaging platform which has been developed in Switzerland and is a paid open-source end-to-end encrypted instant messaging application for iPhone and Android smartphones.

The source said that on Threema like so many other secure applications, a user does not require to enter an email address or phone number to create an account, thus allowing the user to use the service with a very high level of anonymity.

The source said that Threema also hides all the tracks of the user as it minimises the footprint on servers that route traffic.

The source claimed that on Threema the contacts and messages are stored on user's device, instead of on the server.

He said that Threema offers text and voice messages, voice and video calls, groups and distribution lists as features in the application, thus allowing the terrorists to remain "untraced".

The official said besides the mobile application, there is also a browser-based secure desktop chat option of Threema which also does not log IP addresses or metadata of the user.