WannaCry ransomware attack

WannaCry ransomware attack was a worm that infected many Windows computers around the world on May 2017. The worm had spread malware that encrypted the user's computer data (i.e. scrambled the user's computer data into meaningless information) and demanded affected users to pay $300 Bitcoin within 3 days or $600 Bitcoin within 7 days before all of the affected computer's data is destroyed. The malware had cost the world millions to billions of dollars to fix their servers and computers.
Background.
The WannaCry ransomware attack started in May 14th 2017. After the WannaCry ransomware attack started, companies and universities around the world have researched ways to eliminate spread of the malware. After four days, the malware did not spread any further, and it was now easy to eliminate the malware.
The person who started the ransomware attack was Park Jin-hyok, who is a computer hacker in North Korea. On September 6, 2018, the US Department of Justice charged Park Jin-hyok for helping make the program for the WannaCry ransomware, as well as being responsible for the Sony Pictures hack of 2014.
John C. Demers, the head of the Justice Department’s National Security Division, said in a statement:
Mr. Park, who also went by the alias Pak Jin Hek, is unlikely to see the inside of an American courtroom. The United States has no direct, formal relations with North Korea and did not communicate with its reclusive government ahead of the charges.