Authorities said the hack was likely a “terrorist act” and urged media companies to be “vigilant”, warning that further attacks could not be ruled out.
Interior Minister Bernard Cazeneuve said: “There are a lot of elements that suggest that a terrorist act” was to blame for the shutdown at the Paris-based station, whose programmes are broadcast in more than 200 countries worldwide.
For most of Thursday, the channel was forced to broadcast pre-recorded programmes after what TV5Monde boss Yves Bigot said was a cyber-attack “unprecedented in the history of television.”
“When you work in television… and you find out that your 11 channels are down, of course that’s one of the most dreadful things that can happen to you,” Bigot said.
The hackers took control of the station and its social media operations late Wednesday.
By seizing the IT system, they were able to black out the TV channels for several hours.
The self-styled cyberjihadists also posted documents on its Facebook page purporting to be the identity cards and CVs of relatives of French soldiers involved in anti-IS operations, along with threats against the troops.
“Soldiers of France, stay away from the Islamic State! You have the chance to save your families, take advantage of it,” read one message on TV5Monde’s Facebook page.
“The CyberCaliphate continues its cyberjihad against the enemies of Islamic State,” the message added.
The defence ministry in Paris said it was working to verify whether the documents were genuine.