Around 900 ISIS-related Twitter accounts have been suspended after Anonymous posted a list of them online.
The internet-based vigilantes have already waged cyber war on Isis.
Now the group have delivered their first blow with their warning message ‘expect us!’ placed just above the list of names.
The group wants to ‘unite humanity’ in an effort to bring Isis down after militants took the lives of 129 people on Friday.
While it is easy for members of Isis to set up a new Twitter account, it is hoped the action will cause disruption for the terror group.
Accounts can be hard to find, so each time an account is suspended, the number of followers a person has is likely to be diminished.
They also use Arabic hashtags that are trending to increase how much their tweets are seen.
In the video posted earlier, the member of Anonymous says: ‘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.
‘Expect massive cyber attacks. War is declared. Get prepared.
‘The French people are stronger than you and will come out of this atrocity even stronger.’