Anonymous claims to have attacked several hundred Twitter accounts being used by members and sympathisers of the Islamic State of Iraq and Greater Syria (Isis).
A list posted to Pastebin by the Anonymous subset RedCult detailed many accounts that were no longer available, though some were apparently functioning as normal, and also listed Facebook accounts and email addresses allegedly associated with the group.
"We will hunt you, take down your sites, accounts, [and] emails, and expose you," Anonymous said in a statement directed as Isis.
"From now on, [there will be] no safe place for you online. You will be treated like a virus, and we are the cure. We own the Internet."
Several of the targets had followers in excess of 100,000, with many having gained support since being attacked by Anonymous, though the bulk had fewer than 10,000 followers and many had only several hundred.
"Remember, the terrorists that are calling themselves Islamic State, are not Muslims," RedCult added, referencing another name for the insurgent Muslim group.
The group claims to be a mixture of "hackers, crackers, hacktivist, phishers, agents, spies, or just the guy from next door," with its members drawn from all sections of society.
"We are students, administrators, workers, clerks, unemployed, rich, [and] poor," the group said. "We are hedonists, ascetics, joy riders or activists."