Scotland Yard declined to name the 19 year old man, but LulzSec and identified him as Ryan Cleary. According to LulzSec, he merely operated an Internet Relay Chat (IRC) server used by the group and was not a leader.

"Ryan Cleary is not part of LulzSec; we house one of our many legitimate chatrooms on his IRC server, but that's it," the group said Tuesday in a Twitter message. "Clearly the UK police are so desperate to catch us that they've gone and arrested someone who is, at best, mildly associated with us. Lame."

The group then on two hackers it claimed had leaked belonging to LulzSec. It later invited followers to log into an IRC server to discuss its Operation Anti-Security, an effort to steal and leak classified government information.

LulzSec's very public attacks of computers belonging to the U.S. Senate, the U.S. Central Intelligence Agency and companies such as Sony and the U.S. Public Broadcasting Service have put the group in the public spotlight for weeks now. Although the group claims to be hacking for laughs, law enforcement is taking its activities seriously. "You wouldn't believe how hard people are going after these guys," said one security expert, who spoke on condition of anonymity.

Gaining access to the server logs of the IRC server used by LulzSec, could give law enforcement clues to the identity of the group's members, but to date LulzSec has been pretty good about covering its tracks online, according to security researchers.