The hackers' collective known as Anonymous says it, too, is at war with ISIS. In a series of messages posted on Twitter and YouTube, Anonymous claimed to be "preparing to unleash waves of attacks" on the extremist group, which is also known as the Islamic State, ISIL, or by its Arabic acronym Daesh.
In a video posted on YouTube, a masked activist, speaking in French, announced: "Expect massive cyber attacks. War is declared. Get prepared. Anonymous from all over the world will hunt you down."
Though the latest messages refer to Friday's terrorist attacks in Paris, which left 129 people dead and more than 300 wounded, the Anonymous activists want to be clear that they've been fighting this fight for some time.
But what does an online declaration of "war" really amount to?
"Cyberattacks can have a tremendous impact," cyberwarfare expert David Gewirtz told CBS News. "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."
Those operating under the Anonymous banner have focused in the past on disrupting ISIS's social media recruitment efforts and could try to target the group's other communications networks. One Anonymous tweet Monday claimed the group has taken down more than 3,800 pro-ISIS Twitter accounts.
Despite talk of war, Anonymous -- a loose association of hackers best known for attacking the websites of companies and government agencies whose interests conflict with the free, unfettered spread of information -- is not a disciplined army moving as one against an enemy.
"Anonymous isn't really one group. It's many people operating under one umbrella name," Gewirtz said, though he noted that its threats "can certainly be credible in that we can certainly expect that some Anonymous members decided to take some action."
He also warned of the risk of a group of hackers roaming the Internet to target its perceived enemies without any judicial review or accountability.
"Anonymous, while itself something of a vigilante organization, can pick enemies we also see as enemies, but they tend to knee-jerk reactions that might have unintended consequences," Gewirtz said.