US investigators have revealed that a résumé was used to track down North Korean hacker Park Jin Hyok, who was charged on Thursday over the 2017 WannaCry ransomware attack. Park's résumé and photo was tracked after being forwarded by his superior on free email services including Gmail. Investigators accessed about 1,000 email and social media accounts using about 100 warrants. During the 2017 attacks, known as WannaCry, hackers infected computers with malicious software that encrypted data and demanded ransom payments from users to be released. Park was also cited by US officials as part of a conspiracy that conducted the fraudulent transfer of $81 million from the central bank of Bangladesh in February 2016. The US government has previously said that North Korea was behind the attacks, and North Korea has denied that it was involved.