North Korean cybercriminals turned to bitcoin extortions thanks to the cryptocurrency’s anonymity.

Hackers from North Korea have been stealing over 100 million won ($88,100) in bitcoins every month between 2013 and 2015, South Korean cybersecurity company Hauri told Yonhap.

“Since tracking down the culprits is very difficult, North Korea had jumped on the bandwagon of bitcoin extortion since around 2012,” said Hauri’s representative Choi Sang-Myong.

According to him, since 2015 North Korean cybercriminals have expanded their attacks to other countries. Their targets include organisations from all over the world, mostly those with a lower level of cybersecurity.

Earlier, James Lewis, senior vice president at the Center for Strategic and International Studies, said that North Korea was involved in the last February’s attack on the Bangladeshi central bank when $81 million was stolen.

Since access to the Internet is forbidden for most ordinary North Koreans, some believe that the hackers are connected to the country’s security services. The right to use the world wide web is reserved for national security, foreign embassies and some science and research centres, whereas other citizens use the domestic intranet system Kwangmyong. According to the Korea Institute of Liberal Democracy in Seoul, there is an elite squad of 6,800 state hackers in North Korea who generate an estimated annual revenue of $860 million.

According to Coinmap, there are three retailers in Pyongyang – two restaurants and a bar – accepting payments in bitcoin. All of them are located on Yonggwan street.

Elena Platonova