Attacks on the South Korean exchanges were carried out through so-called spear-phishing attacks, or emailing files laced with malware to specific targets.
Cryptocurrency attacks linked to North Korea first started in 2016, and "marked a departure from previously observed activity of North Korean actors employing cyber espionage for traditional nation state activities".
U.S. based Security researcher FireEye claim that the rising price of Bitcoin in tandem with the increasing worldwide sanctions imposed upon North Korea have lead the rogue country to seek Bitcoin hack attacks as an alternate, low cost way of helping finance the state.
North Korea's telecommunications ministry didn't respond to an emailed request for comments.
Spearphishing involves targeting personal email accounts of employees at the digital currency exchange, then using their passwords to gain access to the company's network.
"Sanctions against North Korea are likely to fuel their cybercrime activity", said Bryce Boland, Singapore-based chief technology officer with FireEye.
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Bloomberg said Tuesday that according to a new report from security researcher FireEye Inc., hackers from Kim Jong-un's regime are increasing their attacks on cryptocurrency exchanges in South Korea and related sites.
Tracking down the culprit of a cyberattack is generally hard, and North Korea has generally denied any part in global cyberattacks, despite being linked to the devastating WannaCry ransomware attack in May.
Many other attacks were pointed out, like in April where the bitcoin exchange Yapizon lost $5 million, or between May and July four more attacks have taken place - Bithumb the largest SK exchange for bitcoin and ethereum has been security breached for personal data and so hundreds of millions were stolen. "Attacks on cryptocurrency exchanges can be a great vehicle to obtain what is ultimately hard currency".
It is estimated to bring $1bn a year through illicit activities, including counterfeiting United States dollar currency, producing narcotics, and even smuggling gold.
As bitcoin and other cryptocurrencies have increased in value in the a year ago, nation states are beginning to take notice. "So you see cryptocurrency exchanges, particularly in South Korea, becoming a logical target".
"Bitcoin and other cryptocurrencies have increased in value in the previous year, nation states are beginning to take notice", FireEye said."Consequently, it should be no surprise that cryptocurrencies, as an emerging asset class, are becoming a target of interest by a regime that operates in many ways like a criminal enterprise".