Updated December 26, 2014, 7:41 p.m. ET

On to the next one.

One day after a group of hackers took credit for compromising the networks of PlayStation and Xbox, they now appear to be targeting Tor, a network that helps its users stay anonymous online.

Tor is not a household name, so any attack on the service would not be felt as widely as the disruption of online play for millions of gamers. But Tor is used by a wide variety of people who seek anonymity online, ranging from political dissidents and whistleblowers to those engaged in more illicit activities.

The hacker group, which calls itself Lizard Squad, announced on Twitter that it would be "testing" a new "0day" — which is shorthand for a security issue that has not yet been addressed.

To clarify, we are no longer attacking PSN or Xbox. We are testing our new Tor 0day. — Lizard Squad (@LizardMafia) December 26, 2014

Tor released a statement through a spokesperson confirming the attack, but said it is being addressed.

This looks like a regular attempt at a Sybil attack: the attackers have signed up many new relays in hopes of becoming a large fraction of the network. But even though they are running thousands of new relays, their relays currently make up less than 1% of the Tor network by capacity. We are working now to remove these relays from the network before they become a threat, and we don't expect any anonymity or performance effects based on what we've seen so far.

The Tor network provides anonymity by routing online activity through a series of different locations — called nodes — that makes it very difficult to track users.

Security experts began noticing issues with Tor early Friday afternoon, when Lizard Squad apparently took control of nearly half the nodes that Tor relies on to provide users with anonymity. It has been theorized that control of a large amount of nodes could allow users to be tracked.

It appears that the group is starting many of its own nodes, which it controls.