LONDON—U.K. authorities charged a second man as part of a broadening investigation into online activist group Anonymous and its offshoot LulzSec.
London's Metropolitan Police, known as Scotland Yard, said they charged 18-year-old Jake Davis on Sunday with five offenses, including unauthorized access to a computer system and conspiring with others to launch online attacks against the website of the U.K.'s Serious and Organized Crime Agency, a British equivalent of the U.S. Federal Bureau of Investigation.
Mr. Davis, who police say uses the online nickname "Topiary," appeared at a central London court Monday. He was released on bail with certain conditions, including wearing an electronic tag, keeping to a curfew and not accessing the Internet. Mr. Davis couldn't immediately be reached.
Authorities allege that Mr. Davis's targets also included computers belonging to Sony Corp. and the U.K.'s Sun newspaper. News Corp., which owns the Sun, also owns The Wall Street Journal.
Police last week said they had arrested a man they identified at that point only as Topiary at his home in the Shetland Islands in connection with Anonymous and LulzSec, or Lulz Security. Police are investigating so-called denial of service attacks, where websites are bombarded with data with the aim of knocking them offline.
The groups have claimed responsibility for a series of high-profile online attacks in recent months against companies and government agencies, including Sony Corp. as well as SOCA and law enforcement-related sites in other countries.
That has led to a global clampdown by law enforcement around the world on participants of the groups. That has resulted in dozens of arrests across the U.S., the U.K., the Netherlands, Spain and elsewhere.
U.K. prosecutors in June charged 19-year-old Ryan Cleary, who had been a prominent figure in Anonymous and then LulzSec, with five computer-related offenses. Authorities allege he infected computers in order to form a computer network, called a botnet, which he then used to launch online attacks against websites including that of SOCA. Essex-based Mr. Cleary, who is out on bail, is cooperating with police, his lawyer has said.

British police also arrested five males, aged 15 to 26 years old, in January, a 22-year-old man in April and a 16-year-old male last week. None of those individuals has been charged.
Last month, U.S. authorities arrested and charged 16 people and raided dozens of addresses, mostly in connection with last year's online attacks against payment company PayPal, a unit of eBay Inc. At the same time, Dutch authorities arrested four males aged from 17 years to 35 years suspected of being involved with Anonymous or an offshoot of it, called AntiSec. That comes on top of two arrests Dutch police made in December. All six individuals have been charged with computer-related offenses.
Anonymous shot to global prominence late last year following the launch of a campaign against companies it said were aiding U.S. efforts to stifle WikiLeaks after the website leaked a trove of classified U.S. diplomatic cables. PayPal, Visa Inc. and MasterCard Inc. all suffered online attacks, for which Anonymous took credit, after they stopped people from using their services to make financial contributions to WikiLeaks.

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