Tom Bossert, homeland security adviser to President Donald Trump, wrote in the Wall Street Journal that the attack was carried out by the North Korean Lazarus Group.

The Lazarus Group was responsible for the 2014 hack of Sony Pictures Entertainment that destroyed files, leaked corporate communications online and led to the departure of several top studio executives. That attack was motived by a film which took the mickey out of the North Korean Dear Leader Kim Jong-un.

Bossert said that North Korea has acted especially badly, largely unchecked, for more than a decade, and its malicious behavior is growing more egregious. “WannaCry was indiscriminately reckless.”

Many security researchers, including the cyber firm Symantec, as well as the British government, have already concluded that North Korea was likely behind the WannaCry attack, which quickly unfurled across the globe in May to infect more than 300,000 computers in 150 countries.

Some think that WannaCry was deployed accidentally by North Korea as hackers were developing the code.

WannaCry was made possible by a flaw in Microsoft’s Windows software, which was discovered by the US National Security Agency and then used by the NSA to build a hacking tool for its own use.

The fact that WannaCry was made possible by the NSA led to sharp criticism from Microsoft President Brad Smith and others who believe the NSA should disclose vulnerabilities it finds so that they can be fixed, rather then hoarding that knowledge to carry out attacks.