North Korea disappeared from the internet at least twice in the past month, with state-run websites becoming inaccessible in what some observers speculated was a distributed denial-of-service attack on the country’s servers. In a report published Tuesday, a lone hacker bent on revenge told Wired that he was responsible for crippling the secretive country’s internet.

The American hacker — who goes by the handle P4x — told Wired he was one of the victims of a cyberattack last year on Western security researchers carried out by North Korean spies. He said he was frustrated that he was a target and that the US appeared to have a lacking response.

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He said the hackers tried to snatch hacking tools and information on software vulnerabilities but he was able to stop them before they could get anything worthwhile. Nonetheless, there was a feeling of resentment, he told Wired.

Read more: Business Insider