Kane Gamble launched a campaign against US intelligence officials when he was 15 (Picture: PA)

A teenage hacker leaked the personal details of over 20,000 FBI and Homeland Security officers, a court has heard.

Kane Gamble, 18, allegedly gained access to the accounts of senior US intelligence officials because he was annoyed at the ‘corrupt and cold-blooded’ American government.

In one shocking breach, Gamble posted ‘I own you’ on a TV in a high-ranking officer’s home.

Gamble was just 15 when he targeted the then CIA chief John Brennan and deputy director of the FBI Mark Giuliano, from his family home on a Leicestershire housing estate.

The schoolboy founded the group Crackas With Attitude (CWA) which went online to claim responsibility for the attacks on numerous email and phone accounts.

Kane Gamble allegedly leaked details of 20,000 FBI and Homeland Security officers (Picture: Central News)

Several sensitive documents were reportedly obtained from Mr Brennan’s private inbox, including a 47-page application for top-secret security clearance.

A Comcast cable TV and broadband account belonging to James Clapper, director of national intelligence under President Barack Obama, was also targeted.

Gamble also gained access to the FBI’s Law Enforcement Exchange Portal, using Mr Giuliano’s credentials.

Prosecutor John Lloyd-Jones QC told a sentencing hearing at the Old Bailey: ‘The group incorrectly have been referred to as hackers.

‘The group in fact used something known as social engineering, which involves socially manipulating people, call centres or help desks, into performing acts or divulging confidential information.’

He hacked the then CIA chief from his bedroom in Coalville, Leicestershire (Picture: PA)

Gamble also used an anonymous Twitter profile to talk to journalists.

Mr Lloyd-Jones said: ‘He told a journalist, “It all started by me getting more and more annoyed at how corrupt and cold-blooded the US government are. So I decided to do something about it”.’

To gain his victims’ personal details, Gamble impersonated them, fooling employees at companies such at Comcast and Verizon to divulge personal details.

He used the phone numbers to call and taunt his victims and their families, and take control of their devices, including iPads.

Last October, Gamble, of Linford Crescent, Coalville, pleaded guilty at Leicester Crown Court to eight charges of performing a function with intent to secure unauthorised access to computers and two charges of unauthorised modification of computer material.

Gamble, who has autistic spectrum disorder, will be sentenced at the Old Bailey when the hearing resumes at a later date.