The app was launched in 2013 by Pavel Durov, who has been described as the Mark Zuckerberg of Russia, and his brother Nikolai. It includes a “Secret Chats” feature with end-to-end encryption that ensures the only people who will ever see those messages are the sender and the recipient; not even the people at Telegram have access to them.

Laith Alkhouri, director of Research at Flashpoint Global Partners, told CNN that this messaging app is “the new hot thing among jihadists.” ISIS is supposedly using the service to broadcast widespread messages, including the one in which they declared that the Paris attacks were the “first of the storm.”

Alkhouri estimates that ISIS distributes between 10 and 20 statements and videos through their Telegram channel per day. He says that other jihadi-related channels are being used to ask for donations, and donors can even specify which weapons they want their money to go towards.

The value of personal privacy has been called into question following the tragic events in Paris because encryption helps the attackers hide their activity, but an Instagram post by Durov expresses his belief that France is just as responsible for the attacks as ISIS:

I think the French government is as responsible as ISIS for this, because it is their policies and carelessness which eventually led to the tragedy. They take money away from hardworking people of France with outrageously high taxes and spend them on waging useless wars in the Middle East and on creating parasitic social paradise for North African immigrants.

Fortune has reached out to Telegram for comment and will update this story if we hear back.

Update: Telegram said Wednesday that it had blocked jihadist-related channels on its service

This week we blocked 78 ISIS-related channels across 12 languages. More info on our official channel: https://t.co/69Yhn2MCrK

— Telegram Messenger (@telegram) November 18, 2015