"We are Legion. We do not forget. We do not forgive. Expect us."

So goes the cartoon-villain tagline of Anonymous, the amorphous collective entity that started as an ad-hoc identity for Internet trolls and pranksters and, in the last year especially, has become an increasingly politicized engine of online agitation and digital "hacktivism."

Last week, Anonymous took on its most challenging adversary yet—itself—when a splinter faction took control of a critical communications hub, and released information that could be used to track down other members of the secretive organization. The incident has revealed just how hard it is to peer behind the curtain and see what, or more importantly who, Anonymous really is.

Through its escalating acts of hacktivism, Anonymous has taken up causes of broadening social and political importance. Starting last September, there was Operation Payback, which unleashed weeks of distributed denial-of-service (DDoS) attacks on the websites of the Motion Picture Association of America and other foes of Internet piracy. Next came Operation Avenge Assange, which briefly brought down Visa and PayPal websites after those companies cut off donations to the embattled Wikileaks. This was closely followed by OpTunisia, OpEgypt, and other operations aimed at helping Arab protestors topple their repressive governments.

Much of the work of coordinating these campaigns was done on an Internet Relay Chat network called AnonOps, and it was this hub that was highjacked last weekend in what the network's abruptly shut-out administrators called a "coup d'état." The outage didn't last long. By midweek, AnonOps loyalists had begun relocating the network to a new set of domain names and there were rumors of a major counterblow: The infiltration of an 800,000-computer botnet with which the rogue group (consisting, it seemed, of one disaffected AnonOps admin called Ryan, age 19, and a sidekick or two) had threatened to overrun any new Anonymous sites with DDoS attacks. More serious, perhaps, was Ryan's release of the private Internet protocol addresses of hundreds of registered AnonOps users, no minor violation of the anonymity that is both a tactical asset for Anonymous and, in some ways, its raison d'être.

If Anonymous has suffered any lasting damage from the infighting, perhaps it is to a more fundamental aspect of its identity: its cherished image as an utterly decentralized and leaderless force—a hive-minded swarm in which there are no fixed positions of control and no individuals more authoritative than any others.

In fact, it was precisely the perceived divergence of AnonOps from that ideal that the faction said had driven them to attack it. In an interview with U.K. tech-news site thinq_, Ryan and friends dismissed any notion that the site functions leaderlessly. "There is a hierarchy," said Ryan, singling out a core group of 10 fellow moderators who meet regularly in a private chat channel and, he claimed, effectively decide what sites and causes the group will take aim at next. "All the power ... it's in that channel," he said, insisting further that his only intention in shutting down the network was to break up that power by breaking Anonymous's reliance on AnonOps as a communications venue.