The freewheeling online activities of the hacker groups Anonymous and Lulz Security appear to have been curtailed after a concerted international effort led to what could prove the most significant arrests yet.
Anonymous and LulzSec, two hacker groups which are believed to share several senior members, have claimed credit for attacks on Sony, the UK’s Serious Organised Crime Agency and the Sun newspaper website.
But their headline-grabbing exploits have diminished over recent weeks as the legal crackdown seems to have scared many of the groups’ most capable hackers offline.
Chatter among the many Anonymous supporters on Twitter and other less public chatrooms remains as boisterous as ever, but several of the social network accounts associated with the “hacktivist” group’s figureheads have fallen silent.
The Metropolitan Police said on Thursday night that two men in their twenties had been arrested in connection with alleged computer-related offences under the online identity Kayla.
A hacker using that name has been seen by security experts as being at the heart of LulzSec’s operations, although no connection has yet been proved to any real-world identity.
“Kayla, alongside the likes of Sabu, Topiary and Tflow, is considered to be one of the key figures in the LulzSec hacking gang,” said Graham Cluley, a senior technology consultant at security firm Sophos.
Met detective chief inspector Terry Wilson told the Financial Times on Friday that police believe that Kayla is only one person and that they would soon decide which of the pair would be charged.
Scotland Yard officials allege that Topiary was the nickname used by Jake Davis, a teenager from the Shetland Islands, who was released on bail last month after being charged under the computer misuse act as part of the Anonymous investigation. Mr Davis will appear in a London court in January.
A teenager suspected of using the Tflow name was also arrested earlier in the summer, then released on bail.
This week’s arrests are the latest in a worldwide swoop which has seen the Met collaborate with the Federal Bureau of Investigations and other law-enforcement bodies.
Mr Wilson, the operational lead for the Met’s e-Crime unit, credited a funding increase that has taken his staff from 15 to 83 in three years. “Two years ago, none of these people would have been arrested,” Mr Wilson said.
That deterrent may finally be working. Sabu, another chatroom identity who has claimed credit for some of LulzSec and Anonymous’ most serious attacks, has not been seen online in his or her usual guise for two weeks.
One former Anonymous associate told the Financial Times that Sabu was “MIA”. “He hasn’t even checked in with his closest friends,” the person said.
A final posting on Sabu’s Twitter account appeared to reference the 1995 crime thriller, The Usual Suspects: “The greatest trick the devil ever pulled was convincing the world he did not exist. And like that . . . he is gone.”
Two people familiar with the FBI probe said that the agency is no longer worried about Sabu, suggesting that he has at least been identified and located, if not arrested.