North Korea suspected in hack that bankrupted Bitcoin exchange Youbit

A collection of Bitcoin (virtual currency) tokens are displayed in this picture illustration taken December 8, 2017. REUTERS/Benoit Tessier/Illustration - RC1C93CBDB30

South Korean officials suspect North Korea's involvement in the hack that brought down a Seoul-based cryptocurrency exchange earlier this week.

Tuesday's attack against Youbit would be the latest in a string of successful high-tech attacks by the secretive regime, which has increasingly turned to cyberwarfare as it faces increased economic isolation and costly sanctions, the Wall Street Journal reported.

Youbit said on its website that hackers had pilfered 17 percent of its total assets. It did not elaborate on the total value of the seized assets.

The company quickly announced that all users' remaining assets would be marked down to 75 percent of their value, which clients could withdraw. It also suspended all trading and filed for bankruptcy.

Youbit was hacked in April in a separate attack that South Korean officials linked to North Korea, Reuters reported. Nearly 4,000 bitcoins were stolen in that incident.

Kim Jong Un’s cyber henchmen, who pilfered $81 million last year from an account of the Bangladesh Central Bank, have increasingly used hacking as a means of raising money.

The new approach may be a result of financial pressures. North Korea will probably begin experiencing the effects of the U.N. sanctions that were adopted in September by March 2018, the Institute for National Security Strategy said, according to South Korea's Yonhap News Agency.

The national security institute is affiliated with South Korea's National Intelligence Service.

“In addition to further toughened sanctions, an increase in North Korea's investment in conventional forces in the aftermath of military pressure stemming from the (South Korean) deployment of American strategic assets is forecast to hit the North Korean economy seriously sometime after March next year," the institute said.

The Trump administration has blamed North Korea for other recent cyberattacks, ratcheting up already high tensions between the two nations.

Homeland security adviser Tom Bossert wrote in a Wall Street Journal op-ed published Monday night that North Korea was "directly responsible" for the WannaCry ransomware attack and that Pyongyang will be held accountable for it.

And a South Korean lawmaker in October said North Korean hackers stole highly classified military documents that include U.S.-South Korean wartime "decapitation strike" plans against the North Korean leadership.

South Korea also last year accused North Korea of hacking the personal data of more than 10 million users of an online shopping site and dozens of email accounts used by government officials and journalists.

The United States in 2014 formally accused North Korea of hacking Sony Pictures Entertainment over the movie "The Interview," a satirical film about a plot to assassinate North Korea's leader.

North Korea on Thursday denied that Pyongyang is linked to any cyber attacks.

The Associated Press contributed to this report.