North Korean leader Kim Jong Un giving field guidance at the Sci-Tech Complex in an undated photo released by North Korea's Korean Central News Agency in 2015. Reuters/KCNA North Korean hackers stole about 100 million Korean won, or $88,000, worth of bitcoin from South Korean exchanges every month from 2013 to 2015, Yonhap News Agency reports, citing Radio Free Asia.

"Cyber criminals have turned to bitcoin for money as it is very difficult to track them down," Choi Sang-myong, a senior official at South Korea's cybersecurity firm Hauri, told Free Asia Radio, according to Yonhap. "Since tracking down the culprits is very difficult, North Korea had jumped on the bandwagon of bitcoin extortion since around 2012."

The apparent theft comes as North Korea looks for ways boost its hard currency amid an onslaught of sanctions levied against leader Kim Jong Un's regime, according to Radio Free Asia.

It's not the first report of hacking from North Korea aimed at the capital markets. North Korean hackers have been accused of transferring almost $1 billion from Bangladesh Bank's account at the New York Fed by using the Swift messaging network in February of last year.

The latest report comes at an interesting time for the cryptocurrency.

Last month, the US Securities and Exchange Commission rejected plans for two bitcoin exchange-traded funds, partly because of security concerns.

In its ruling on the ETFs, the SEC said: "Based on the record before it, the commission believes that the significant markets for bitcoin are unregulated."

It continued: "Therefore, as the exchange has not entered into, and would currently be unable to enter into, the type of surveillance-sharing agreement that has been in place with respect to all previously approved commodity-trust ETPs — agreements that help address concerns about the potential for fraudulent or manipulative acts and practices in this market — the commission does not find the proposed rule change to be consistent with the Exchange Act."

The cryptocurrency is, however, gaining acceptance elsewhere. Japanese regulators ruled that as of April 1, bitcoin would be accepted as a legal payment method. Additionally, on Monday, Russia said it would consider recognizing bitcoin and other cryptocurrencies in 2018.

Bitcoin has been the top-performing currency every year since 2010, aside from 2014. It's up about 25% in 2017.