It's (cyber) war against the Islamic State.

The New York Daily News noted that a member of YouTube vigilante group, Anonymous, has posted a video on Friday following the Paris attacks, vowing to launch "massive cyber attacks" while donning the group's feature Guy Fawkes mask in a two-minute clip.

The member, whose voice perceive him to be male, said, "Expect massive cyber attacks. 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," he threatened.

However, the latest message from Anonymous, as noted by CBS, refers to Friday's attacks the activists made clear that they have been fighting against ISIS for some time now. Reading from as script as newscasters do, the video also showed black and white clips of what are said to be the response to the terrorist attack in the city.

The man finished the video by saying, "The French people are stronger than you and will come out of this atrocity even stronger."

That said, what effect could a cyber declaration of war have against a definitely non-cyber war?

Cyberwar expert David Gewirtz noted that "Cyberattacks can have a tremendous impact."

"Of course, they can't be used to arrest people or take terrorists off the field, but they can certainly be used to compromise structural components of terrorist operations. More to the point, they can go after both the money that terrorists have and their funding sources. Damaging the money flow can certainly have an impact on the terrorists' operations," he shared.

It's not the money that Anonymous has attacked in the past, though. Those operating under their banner has focused on disrupting the terrorist group's recruitment efforts by targeting their social media and communication networks. As of Monday, the group has claimed to have taken down more than 3,800 pro-ISIS Twitter accounts.

To clear things up, Gerwirtz noted that Anonymous isn't one group, but rather, many people operating under an umbrella name. However, he did acknowledge that their threats "can certainly be credible in that we can certainly expect that some Anonymous members decided to take some action."

There are also risks to hacktivists group like Anonymous, as Gerwirtz explained, they tend to have knee-jerk reactions to issues with consequences that they do not intend to have, making them risky as a vigilante group in terms of lack of judicial accountability.

Check out the full video from Anonymous below.