Representation of Ethereum, with its native cryptocurrency ether, is seen in this illustration taken Nov. 29, 2021. Reuters-Yonhap

South Korea confirmed Thursday that North Korean hackers were behind the theft of 58 billion won ($41.5 million) worth of cryptocurrency in 2019.

The National Office of Investigation of the National Police Agency announced the finding, saying North Korea's state-sponsored hacking groups Lazarus and Andariel were involved in the theft of 342,000 Ethereum tokens from the cryptocurrency exchange Upbit in November 2019.

The tokens, valued at 58 billion won at the time, are now equivalent to 1.47 trillion won.

This marks the first time a South Korean investigative agency has confirmed North Korea's involvement in cryptocurrency hacking crimes, though similar charges have been raised by the United Nations and other countries.

Police said they were able to confirm North Korea's involvement by tracking IP addresses and cryptocurrency flows, as well as by detecting the use of the North Korean language and analyzing material secured with the help of the U.S. Federal Bureau of Investigation.

Police did not release details of the methods used in the hacking attacks, citing concerns of their recurrence or copycat crimes.

North Korea sold 57 percent of the stolen Ethereum tokens at 2.5 percent below market price in exchange for bitcoin tokens on three cryptocurrency exchange websites presumably established by the North, according to police.

The remainder of the Ethereum was distributed to 51 overseas exchanges and laundered, they said.

In 2020, a portion of the stolen cryptocurrency was discovered on a Swiss cryptocurrency exchange, and after proving their source to the Swiss prosecution over four years, police said they returned 4.8 bitcoin worth around 600 million won to Upbit last month. (Yonhap)