Hackers acting in support of Islamic State extremists knocked out the global broadcast network of France's TV5 early Thursday, then hijacked its website and social media to post warnings against French participation in air strikes against the militants in Iraq and Syria.
The computer system of TV5 Monde, whose Facebook page says it reaches 257 million households in 200 countries and territories, was invaded by malware late Wednesday that took over the network's transmission server and blocked its satellite signal, network executives told French and international media.
All 11 channels went black for three hours until prerecorded programming was directed to fill viewers' blank screens, said TV5 Monde Director General Yves Bigot.
"For the moment, we are unable to produce our own programs," Bigot told France-24 television, calling the attack "unprecedented in the history of television." He said one television channel had been restored but it would be hours, possibly even days, before the entire network was again functional due to the need to scour the systems for residual infection.
The hackers also temporarily controlled TV5's Facebook page and other social media accounts. For two hours before the network recovered those sites, an image of a masked militant filled the page under the title "Cybercaliphate" and the French phrase "Je SuIS IS," a co-opting of the message of unity -- Je suis Charlie [I am Charlie] -- proclaimed by millions in France in solidarity with those slain by Islamic extremists at the Charlie Hebdo satirical magazine in Paris on Jan. 7.
Another post warned that French President Francois Hollande committed "an unforgivable mistake" by joining Western forces in attacking Islamic State, adding that the offensive is "a war that serves no purpose."
Other material posted on the network's social media while they were under the hackers' control included identity cards and resumes of family members of French soldiers deployed with the international coalition that has been waging airstrikes against Islamic State fighters in Iraq and Syria. The militants control about one third of the territory of those two countries and have proclaimed a "Caliphate" committed to invoking a harsh and medieval version of Islamic law.
"Soldiers of France, stay away from the Islamic State!" a message on the network's Facebook page read overnight. "You have the chance to save your families, take advantage of it."
The posting of individuals' identity cards appeared to be a warning to French troops involved in the anti-Islamic State coalition that the militants know how to reach their families and harm them.
More than 1,500 militant Muslims of French origin or residency are believed to be fighting with Islamic State, providing the group insight and contact with broad sectors of the French public.
Wassim Nasr, France-24's expert on jihadist movements, observed that some of the hackers' Arabic-language Internet postings contained numerous spelling and grammar mistakes, suggesting that "the authors are not Arabic."
The Paris prosecutor's office announced that an investigation had been launched to identify the perpetrators of what it called a terrorist attack.
French Prime Minister Manuel Valls joined other government officials in showing solidarity with the hacked network by visiting the Paris headquarters. He called the hacking an "unacceptable attack on the freedom of information and expression."
"We are up against determined terrorists," Interior Minister Bernard Cazeneuve told journalists, vowing that "we are determined to fight them."