Under its #OpParis operation, hacktivist group Anonymous has taken down more than 5,500 Twitter accounts related to ISIS members and associates.

After the killing of 129 people in Paris on Friday, the organisation waged cyberwar on ISIS with a cautionary video posted online. The vigilante recording features a member of Anonymous, disguised in the signature Guy Fawkes mask, reading the following message:

“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.”

The suspension of enthusiast Twitter accounts seems to be the first move in the proposed action. In a document published after the massacre, Anonymous wrote: ‘Operation ISIS Continues […] We Are: Muslims, Christians, Jews […] We come from all races, countries, religions, and ethnicity. UNITED AS ONE, DIVIDED BY ZERO…

ISIS: We will hunt you, take down your sites, accounts, emails, and expose you. From now on, (there will be) no safe place for you online. You will be treated like a virus, and we are the cure.’

Although it is simple for IS enthusiasts to create a new online profile, the Anonymous action aims to cause disruption for the terrorist group. With each suspended account, the number of followers is likely to take a drastic hit.

Through the site #opIceISIS, anyone can search the existing database and index new social media accounts related to terrorist activity. The entry form includes fields for name, location, picture, Twitter, Facebook and YouTube account details.

However as cyber security experts have pointed out, the work of the hacktivists could be counter-productive to police investigations. “To close those accounts is to leave police deaf and blind around some matters,” said [French] security blogger Olivier Laurelli.