LONDON — As suspects go, Ryan Cleary did not look dangerous: a pale 19-year-old who looked five years younger, wearing a white skateboarding T-shirt and track pants, standing nervously in a courtroom here on Thursday.

But charges by the British police link Mr. Cleary to a hacking group called Lulz Security, or LulzSec, which has been on an Internet crime spree in recent weeks, attacking Web sites and computer networks including those of the United States Senate, the Central Intelligence Agency and Sony.

The British tabloids have been quick to cast Mr. Cleary as the young criminal mastermind behind LulzSec, calling him “Hack the Lad” in front-page headlines. His mother, Rita, has said her son is highly intelligent but has a history of mental illness, including agoraphobia. His lawyer, Ben Cooper, described Mr. Cleary as “a vulnerable young man.”

Though it is not clear how much notoriety he deserves, Mr. Cleary’s arrest has made him a focus of the public fascination with a wave of computer hacking cases, carried out by amorphous online collectives.