A teenager suspected of recording calls to a Scotland Yard counter-terror hotline is facing a second night of questioning.
The teenager being held is though to be a hacker known as TriCk, the leader of the hacking group TeaMp0isoN, a 17-year-old Muslim who has previously claimed to be British.
He was transferred from the West Midlands to face police interviews in central London as a 16-year-old was released on bail over the alleged "phone bombing" campaign.
Both boys, thought to be members of online group Team Poison, were held on suspicion of offences under the Malicious Communications Act and the Computer Misuse Act after phone recordings appeared on YouTube.
The pair were arrested last night when Team Poison claimed it eavesdropped on highly-sensitive conversations after using bypassing technology from the 1980s.
"It wasn't a hard hack at all," TriCk said in an exclusive interview with the Huffington Post UK.
"It was actually easy, you just have to learn how phone systems work and learn the art of phreaking, which most so-called hackers these days don't even read about. Nor do they even know what phreaking is, except for the underground that is."
Scotland Yard's Central e-Crime Unit (PCeU) said it was aware hoaxers had made calls to the hotline and made recordings of their conversations with anti-terrorist hotline staff.
A spokesman said the 17-year-old "has now been brought to a central London police station" while the 16-year-old "has been bailed to return to the police station in the West Midlands pending further inquiries".
A statement added: "Public reporting is an important part of the fight against terrorism and any attempt to disrupt this service will be investigated thoroughly."