The loophole could have provided North Koreans with unrestricted access to international phone calls and Internet access and relied on the prepaid SIM cards that have been available to tourists since February 2013.
The cards, purchased upon arrival in Pyongyang, provide visitors with access to a part of the 3G network reserved for foreigners and those in powerful positions.
Typically, North Koreans that can afford a mobile phone can only make domestic phone calls and have no international Internet access from their handsets. The restrictions mirror domestic phone lines in houses, which cannot make or receive calls from overseas.
The two-level telecommunications system is a key part of the information blockade imposed on North Koreans by their government. Foreign radio services are jammed so they are difficult to hear, foreign newspapers and magazines are not available and satellite TV is banned.
Until recently, visitors who purchased the SIM cards were able to leave Pyongyang with credit left on their cards. But now, according to tour companies that regularly visit the country, that policy has changed and the cards must be deactivated upon departure.
That meant the government had essentially lost control of the SIM cards, which could theoretically have been sent back into the country and given to North Koreans. The cards would have provided international communications at least until the credit had run out and the government would have only been able to trace them back to tourists, who had already left the country.
If the cards have been used this way is unclear. Any group sending SIM cards in would have done so in secret to avoid just such a policy by Koryolink.
For tourists, the change means little unless they were planning to return and utilize any of the remaining credit.
So, for now, the only way for North Koreans to get access to unmonitored international phone lines and Internet while inside the country is to make the journey to the country’s border with China. There, Chinese cellular networks can be accessed, although it still requires a Chinese SIM card.
For the last several years, North Korean authorities have been stepping up their monitoring of such calls made from border areas. As a result, activists says calls have to be kept under 3 minutes in length to avoid getting caught.