A teenage hacker made £386,000 selling malware to criminals that was used in more than 1.7 million cyberattacks around the world.
Adam Mudd, now 20, developed Distributed Denial of Service (DDoS) software called Titanium Stresser which let users crash websites and computers by flooding them with data.
Mudd, who lived at home with his parents in Kings Langley, Hertfordshire, sold the software to online criminals who caused damage to firms worth millions of pounds.
Mudd is appearing at the Old Bailey on computer offences. Jonathan Polnay, for the Crown, said the defendant's hacking programme affected almost every major city in the world along with major companies such as Microsoft and Sony.
The teenager, who has Asperger's syndrome, raked in almost £400,000 by the time he was 18 by selling the programme to criminals between 2013 and 2015.
He received a total of £240,153.66 and 249.81 bitcoins - worth an overall £386,079, the court heard.
Mudd, who was studying computer science at West Herts College, was said to be more interested in status than the money.
At the hearing he admitted security breaches against his own college and 70 more schools and colleges, including Cambridge University and the universities of Essex and East Anglia as well as local councils.
Polnay said: "This was not a 'white hat', friendly test to see what was going on." The term "white hat" is used for ethical hackers who test cyber security on the web.
The court heard how more than 112,000 people registered to use Titanium Stresser. It hacked over 666,000 IP addresses including 53,000 from the UK.
The fantasy game, RuneScape, suffered 25,000 attacks and cost the company that made it £6m trying to defend itself against the attacks.
The software was created in September 2013 and registered under a fake name and address in Manchester. Sixteen different computer servers were used to host the TitaniumStresser.net site over two years.
Polnay added: "This is a young man who lived at home. This is not a lavish lifestyle case. The motivation around this we tend to agree is about status. The money-making is by the by."
Mudd was arrested in March 2015 while on the computer in his bedroom.
He has pleaded guilty to one charge of carrying out unauthorised acts with intent to impair the operation of computers, one of making, supplying or offering to supply an article for use in an offence contrary to the Computer Misuse Act, and one count of concealing criminal property.
He is due to be sentenced next week.