Islamic State followers have migrated to a new messaging service following a purge on their preferred platforms, where they continue to communicate and share propaganda.
Isil had used encrypted messaging app Telegram, but jihadists have begun opening up accounts on relatively unknown service TamTam.
A joint initiative between social networks, including Telegram, Google, Facebook and Twitter, as well as the EU law enforcement agency Europol, last week led to one of the biggest crack downs to date on channels linked to the groups.
Nearly 5,000 accounts and over 26,000 items, including videos, publications, social media accounts and communication channels deemed to be terrorist propaganda, were shut down.
Isil used its Nashir News Agency channel on TamTam to issue a claim of responsibility for the London Bridge attack over the weekend.
TamTam acts as a private messaging application but also has a "channels" function like Telegram, which allows users to broadcast their messages to an unlimited audience. The free chat and video call messaging app is available on both Google Play and the App Store.
It was launched in 2017 and operates through a Russian social networking platform called Odnoklassniki, which is owned by the Russian company Mail.Ru.
"For the time being, for as far as we know, IS is not present on the internet anymore and we will see how fast, if ever, they will regain service," Eric Van Der Sypt, Belgium’s Federal Prosecutor, said at a press conference on November 25.
Amarnath Amarasingam, a research fellow at the Institute for Strategic Dialogue, cautioned that it would not be easy to root out the group for online platforms.
“A week after his announcement, I woke up with 1,200 messages on TamTam from almost 100 ISIS channels,” he said.
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he told the Telegraph followers are experimenting with a whole host of platforms from Hoop, to Rocket Chat, to Riot. "There is also an active debate happening in supporter networks about the pros and cons of all these platforms," he said.
“TamTam has already started taking down some accounts, but Isis supporters are creating so many new channels it is hard to keep up.”
Mr Amarasingam warned that an attempt to drive Isil followers offline could make it harder for governments to monitor their activities.
“The negative implications of this are significant. It could mean that governments will be left in the dark about what the Islamic State is saying and doing online, particularly as it morphs into a new, post-territorial insurgency in the wake of the loss of its physical caliphate and appointment of its new caliph.”
Quraysh, a pro-Isil media group, warned Telegram that its purge would only drive jihadists underground where the authorities could not see what they were doing.
TamTam has begun a smaller purge on some of the accounts, but many were still active when the Telegraph checked on Tuesday.
A spokesman for TamTam said: “We are strongly against the presence of any sort of content by terrorist organisations on our platform. TamTam’s licence agreement stipulates a ban on the promotion of violence, extremism and terrorism. Every user can help us to clear up the platform, as one can report any chat or channel and our support team will promptly respond.”