The computer hacking group Anonymous have declared war against ISIS, announcing that they will launch "massive cybere attacks" in a YouTube video posted in response to Friday's attacks on Paris.

Donned in the group's feature Guy Fawkes mask, a secret member spoke in French during the 2-minute clip.

"Expect massive cyber attacks," he said. "War is declared. Get prepared. Anonymous from all over the world will hunt you down. ... You should know that we will find you and we will not let you go. We will launch the biggest operation ever against you. ... The French people are stronger than you and will come out of this atrocity even stronger," the man finished.

The group also used Twitter to threaten ISIS.

"We're also better hackers," warned the group, who also said "there will be nothing left" of ISIS propaganda sites after Anonymous finishes with them.