Charlton Floate, 19, caused government websites in the UK and one used by the FBI to crash.
Part of a team of hackers, Floate was working from the family home in Solihull and took control of other people's computers. The Birmingham Mail reports that he bragged about the group's success on the internet.
Floate has admitted three charges under the Computer Misuse Act and three of possessing forbidden images.
Floate had carried out two test runs when he hacked into computers of two men in the US in November 2012.
Kevin Barry, prosecutor at Birmingham Crown Court, said that in January 2013, Floate and others targeted the highly used Home Office website that provides information on subjects including passports and immigration, as well as a site used by the FBI that allows people to report crime.
By infecting other computers with malware, the team was able to target the sites with massive digital traffic causing them to crash. Floate had bragged about the attacks on an internet forum and Twitter. Police linked him to the occurrences when he used his IP address to check the effectiveness of the attacks.
Barry said there was also evidence that Floate attempted to recruit another person into the scheme. However, he stated that Floate was “at the heart of the conspiracy” and was the central player.