A 17-year-old boy has admitted seven hacking offences linked to the TalkTalk data breach in October 2015.

The teenager, who cannot be named for legal reasons, was arrested in Norwich on November 3 last year and charged with breaching the Computer Misuse Act 1990 following an investigation by the Metropolitan Police's Cyber Crime Unit.

He admitted the seven charges when he appeared at Norwich Youth Court on Tuesday. Sentencing was adjourned to December 13.

Read more: Brave shopkeeper fends off Irn Bru bottle thug with a broom during botched raid at Gourock shop

Telecoms giant TalkTalk fell victim to what it described as a ''significant and sustained'' attack on its website on October 21, 2015.

The attack resulted in the personal data of nearly 160,000 people being accessed and was branded a ''car crash'' earlier this year by then information commissioner Christopher Graham.

The Information Commissioner's Office fined the firm a record £400,000 last month for security failings that it said had allowed customers' data to be accessed "with ease". The ICO said that in 15,656 cases, bank account details and sort codes had been accessed.

Read more: Woman sexually assaulted 'hundreds of times' by her babysitter urges victims to speak out and spare themselves torment

In July, the firm said the fallout from the cyber attack had cost it £42 million.

Laura Tams, prosecuting, said the charges stemmed from the high-profile cyber attack on TalkTalk, but also included attacks on other websites, including Manchester University, Cambridge University and that of Merit Badges, a small family company that supplies martial arts badges.

"(The youth) was identified as having been involved in the TalkTalk matter, Metropolitan Police officers attended his home address and conducted a search of that and identified electronic devices that they took away for view.

"From that they identified the further offending that you see in front of you today.

"He was using a software programme called SQL map, which the prosecution say is a hacking tool used to identify vulnerabilities on a website."

Read more: Police close lane of A14 in search for missing RAF man Corrie McKeague

She said the tool is "legitimate software" which gives a legal disclaimer warning users that it must only be used to identify vulnerabilities on websites with mutual consent.

In the days before the TalkTalk hack, the youth gained access to a database of 693 staff and students at Manchester University containing email addresses and identity numbers which a "more capable hacker would be able to use for wider criminality", Ms Tams said.

He then attacked a library website belonging to Cambridge University, but both universities traced the IP of the computer used back to the teenager's home address.

More than 600 attempts to hack the TalkTalk website were made in the days before the breach and a person who was not the teenager attempted to download a database, Ms Tams said.

In a Skype conversation on the day of the breach, the teenager told a friend: "I'm going to get f*****."

He added that he had "done enough to go to prison".

Read more: Brave shopkeeper fends off Irn Bru bottle thug with a broom during botched raid at Gourock shop

The teenager posted the TalkTalk vulnerability on a website, showing others how to access it.

"Anyone could go on there to immediately identify where the vulnerability was," said Ms Tams.

She said the TalkTalk website was targeted more than 14,000 times after details were posted.

Ms Tams said the teenager claimed in an online conversation that he "could potentially have everyone on TalkTalk" and then mentioned "wiping and nuking his digital devices".

Referring to the hack on the martial arts badge website, she said the teenager discussed putting an offer code on the website to give a 100% discount.

A link to a photograph of the teenager and his website was found on the site of one of the universities he targeted, Ms Tam said.

"(The teenager) was the only youth who has been charged in relation to the TalkTalk operation," said Ms Tams. "The others charged are adults and I propose to say no more about that."

Chris Brown, mitigating, said more than 700 pages of evidence were served by the Crown Prosecution Service.

He said the world of computers was a mystery to most people, but cyber crime should not be seen as a special form of criminality and there were different degrees of offending.

"It's not the prosecution case that what happened at TalkTalk lies solely at his door," he said.

He said that the vulnerability on the TalkTalk website had been talked about before the teenager accessed it, and he said the teenager's motives were important.

"That vulnerability was seized upon by someone who a matter of days previously had found a way of hacking another type of business," said Mr Brown.

"That company had its customer database seized, those customers were threatened with requests for money so their details weren't sold on the dark web, and the company was asked to pay a ransom to prevent that happening.

"That's not [the teenager]. That's someone acting completely apart from him.

"That person used the vulnerability in TalkTalk days later to demand things and emailed the chief executive of TalkTalk with similar blackmail efforts."

He said there was a "ladder" of hackers, including ethical hackers who discovered vulnerabilities, privately emailed website owners and helped them to fix issues.

"You're dealing with someone who at the time was just 16 years old, who created a number of personas online," said Mr Brown. "Personas that talked about his abilities as a hacker."

He said the teenager was challenged to prove he had done the things he claimed to have done when posting online messages, and was sometimes "called out".

"There are other websites where he was called out as someone who exaggerates his prowess and is either called out or ceases to be involved in the conversation," said Mr Brown.

He said that after the teenager hacked the martial arts badge website he successfully created a 100% discount link, shared it with one friend, posted "LOL" but did not use this to harm the business.

"The thrill was in the chase," said Mr Brown. "It was not in damaging their website or causing loss to them. It was playing."

He continued: "It's inexplicable to the rest of us - why get in so much trouble for what's bravado, to prove you can, to prove you've got the skills.

"You have somebody who becomes a personality online."

Mr Brown said the teenager's part in the TalkTalk breach was "signposting".

The teenager, who admitted he knew his actions were illegal, told magistrates: "I didn't really think of the consequences at the time.

"I was just showing off to my mates."

Asked about his interest in computers, he added: "It was a passion. Not any more. I'm very careful nowadays what I do.

"I realise what I've done is really significant and it won't happen again. I've grown up."

A photograph found on one of the teenager's computers showed a desktop set-up with three computers, the court heard.

Detective Constable Mark Roberts, who was the investigating officer, confirmed that an iPhone, a USB stick and an Apple Mac Air were seized but two of the three computers were unrecovered.

The teenager sat with his parents and his grandfather in court.

Magistrates asked the teenager's father why he had three computers, and he replied that his son had a keen interest in computers but "a lot of it went over my head to be honest".

Chairman of the bench Jean Bonnick said magistrates were minded to spare the teenager jail, but that further reports were needed first and that early discussions would not bind the decision of the sentencing bench.