"As we have clearly stated on several occasions, we have nothing to do with cyber attack and we do not feel a need to respond, on a case-by-case basis, to such absurd allegations of the US", the spokesman said, according to the North's official KCNA news agency.
"After a careful investigation, the United States publicly assigns the massive WannaCry cyber-attack to North Korea", Trump's adviser announced.
The WannaCry virus infected computers in May around the world, including Japan.
The latest accusations against the communist government only heighten the tensions between the USA and North Korea, which have been battling for months over North Korea's nuclear and missile program.
Vipin Narang, a political science professor at the Massachusetts Institute of Technology, said on Twitter that "the notion in DC that you can give North Korea a "bloody nose" without the U.S. or an ally suffering a severe stab wound in return is delusional".
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Despite the lack of notice, some parents were able to pull their kids from class once they were told of Ivanka's visit. An alumni of the academy, Monica Mercuri , also expressed her disapproval.
It also warned other nations against "unreasonably following the footsteps of the US".
"The attack was widespread and cost billions, and North Korea is directly responsible", Tom Bossert, Homeland Security adviser to the current administration, wrote in an article published on Monday, Dec. 18.
United States homeland security adviser Tom Bossert wrote a Wall Street Journal op-ed published on 18 December that claimed North Korea was directly responsible for the cyberattack. Foreign Office Minister Lord Ahmad said in a statement that, "The UK's National Cyber Security Centre assesses it is highly likely that North Korean actors known as the Lazarus Group were behind the WannaCry ransomware campaign - one of the most significant to hit the UK in terms of scale and disruption".
Those possible responses include destroying a launch site before North Korea could test a missile, as well as targeting a stockpile of weapons, according to The Telegraph.
Security firm FireEye believes U.S. sanctions against North Korea are fueling its interest in Bitcoin and cryptocurrencies.