British police have arrested a 16-year-old boy in London over a cyberattack on telecoms firm Talk Talk.The Metropolitan Police said Friday that the teenager was held on suspicion of computer misuse. He has been bailed pending further inquiries.A 15-year-old boy arrested earlier this week in Northern Ireland over the attack also has been released on bail.Talk Talk initially said private information on its 4 million customers might have been stolen in the attack last week. But it later said the hack wasn't as bad as feared and customers' credit card information had not been exposed.The firm said it received a ransom note from the alleged hackers.It is the third known cyberattack this year on Talk Talk, which provides mobile phone, Internet and pay-TV services.