When you're developing intercontinental ballistic missiles and nuclear weapons while under some of the harshest economic sanctions the world has seen, every bit—and every bitcoin—apparently helps.

North Korea has been implicated in both the WannaCry cryptographic worm and its bitcoin ransom demands as well as stealing about $81 million in traditional money through fraudulent funds transfers from a Bangladeshi bank. And now it appears that North Korean hackers are responsible for bringing down the Youbit cryptocurrency exchange in South Korea.

Police investigators and the Korea Internet and Security Agency are viewing the case as an extension of the April attack, Bloomberg reported, citing a person familiar with the investigation. Authorities said they are open to all other possibilities besides the Pyongyang regime, the person said Thursday.

The investigation is looking into the hack of a South Korean cryptocurrency exchange Youbit on Tuesday which led to its collapse.

Yapian, the company that operates Youbit, filed for bankruptcy after Tuesday’s attack.

People familiar with the situation said there are telltale signs and historical evidence that North Korea was behind the Youbit attack.

Senior director at the Korea Economic Institute in Washington, Troy Stangarone: “North Korea is an ideal country to use hacking and financial tools like bitcoin