Now it has leaked details of at least five men it claims are recruiters for the terror group, as well as taking down 5,500 Twitter accounts.
Mirror Online has seen the names, addresses and phone numbers of men living in countries including Afghanistan, Tunisia and Somalia.
Anonymous activists also claimed to have identified a "high-ranking" recruiter living in Europe, but have not yet published an address.
We have contacted some of the men who have been named, but they have not replied and we have been unable to verify if the allegations against them are true.
Hitting these accounts is seen as a way of shutting down the ISIS recruitment and propaganda machine.
A group of hackers called GhostSec is also working feverishly to identify the Paris attackers.
"We have been flooded with data," a source told us.
Yesterday, the hackers released a video which warned: "You should know that we will find you and we will not let you go."
"Expect massive cyber attacks. War is declared.
"Get prepared."