Analysts say the explosive growth in the value of bitcoin makes it and other "cryptocurrencies" an attractive target for North Korea, which has become increasingly isolated under worldwide sanctions imposed over its nuclear weapons and missile programs.
He said North Korean hackers were still at work last week, and were shut down by a retaliatory response by the US and others. The North has dismissed the accusations.
The WannaCry attack was one of the most devastating acts of cyberterrorism in recent times: the fast-spreading malware locked down several computers in the UK's NHS hospitals and displayed a message prompting users to pay $300 in Bitcoin to decrypt the files and restore them to working order - before spreading to 150 countries.
In response to a question from a reporter, Bossert said that government cooperation would obviously include cooperation with "countries bordering North Korea"-meaning mostly China-to help to deny North Korea's agents the ability to run cyber-attacks from outside of their country".
"They shut down accounts the North Korean regime hackers used to launch attacks and patched systems", he said. According to experts, it had caused billions of dollars of damage.
But that amount could now be worth about 90 billion Korean won ($82 million), Moonbeom Park, a researcher at the Korea Internet and Security Agency, told Reuters. The UK had also previously accused North Korea for the outbreak.
The attacks this year began by targeting the companies themselves, stealing customers' personal information, including names and email addresses, Park said.
It also allows the U.S. to galvanise the private sector, he said, adding that in this case, the private sector also acted.
Meanwhile, Microsoft president Brad Smith, in an interview with ITV News at Microsoft's headquarters in Redmond, said Pyongyang was behind the ransomware attack. "Stopping malicious behavior like this starts with accountability", Bossert said. But as far as direct measures against North Korea go, the US' options are very limited.
While North Korea is the main focus of Bossert's claims in the Op-Ed, he does not forget to talk about alleged 2016 election meddling by Russian hackers or the US's issues with Iran either.
After the hack of Sony Pictures Entertainment, the Federal Bureau of Investigation announced that it had proof that North Korean hackers had launched the attack.
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