10 ways North Korea uses technology to keep its citizens in the dark about the outside world

North Korea isn't totally cut off from everyday innovations like mobile data or smartphones. Citizens can buy smartphones that were manufactured in China, but are distributed under a North Korean brand name. The phones look a lot like the cheap Android phones you could buy in any shop — but these come pre-loaded with spyware and software tailored by the state.

Alternatively, citizens can buy their own unlocked devices smuggled across the Chinese border, but they face being tracked via North Korea's mobile network.

It's the same on PCs, with North Korea producing a Linux-based operating system called "Red Star" that can snoop on user activity.

According to Williams, North Korean phones run on Android, the open source mobile software. Engineers have modified the software to include a background program called "Red Flag", which spies on everything a user does and takes screenshots at random intervals to capture their activity. Those screenshots are recorded on a database called "Trace Viewer."

Although North Korea probably doesn't have the resources to check everyone's screenshots, Williams noted that it's a great mechanism to get people to self-censor out of pure fear.

According to the report, North Korean engineers created file watermarking software that essentially tags and monitors any media file that's opened on a device, whether that's a PC or mobile.

Anyone watching a foreign film on their device would have that file tagged and tracked. The tag can track every device on which the file is viewed — so if one person in particular is distributing lots of foreign media with fellow citizens, the regime would probably find out.

North Korea does have a telecommunications system, and the current version is a joint venture with an Egyptian firm called Orascom.

The network is split into two halves, according to Williams' report, meaning both North Korean tourists and foreign citizens can make calls and send texts inside the country — but neither can communicate with the other.

Described as a "firewall", Williams writes that this is set at the account level. He adds that domestic citizens have phone numbers prefixed with 191-260, while phones for foreigners have numbers that begin with 191-250.

Tourist SIM cards have found their way back into the country — so North Korea has begun deactivating them so there's no risk citizens can get hold of SIM cards that let them access the broader internet or foreign calls.

Williams spoke to a number of North Korean defectors, people who fled the regime into China, Japan, or South Korea.

They reported that the regime will put people to death for watching foreign content, especially for anything as illicit as porn, or anything criticizing the Kim family.

"Watching pornography is strongly restricted. I've heard you can get executed for watching pornography," according to one escapee.

An Amnesty International report also found that a man who watched porn with his wife and another woman was executed, with the entire city summoned to watch his death.

Unsurprisingly, few escapees are willing to talk about their porn habits.

But citing a source who knows about illegal smuggling between North Korea and China, Williams states that SD cards containing porn can fetch up to $500. That price reflects both the high demand and the extreme risk of smuggling the material across.

North Koreans buying a radio through official channels will find the device locked only onto government-approved frequencies. Listening to foreign radio, or watching foreign TV, is illegal and the government regularly carries out raids to make sure people aren't consuming anything subversive. (Lots of North Koreans have a second radio or TV which can receive foreign broadcasts and which they keep hidden, and show their "official" device to any inspectors.)

According to Williams, North Korea jams foreign radio signals. This, he writes, involves "transmitting loud noise" on the same frequencies to overpower the broadcast. In particular, North Korea focuses on jamming two stations run by South Korea's intelligence service, called Voice of the People and Echo of Hope.

In a cloistered world where entertainment is low-quality or scarce, food is hard to come by, and the work repetitive and unfulfilling, it's little wonder that foreign films and international TV holds some allure to North Korean citizens.

The state has, according to Williams' report, come up with a softball distraction method: offer homegrown smartphone games.

The report claims there are up to 125 mobile games available to play on North Korean mobile devices, such as "Volleyball 2016" and another title called "Future Cities." The BBC in September reported that North Korea had created a Ronaldo-focused mobile game that was becoming popular.

The idea is this: if citizens spend their leisure time playing domestically produced games (and paying for them), they're not spending their cash on illegally smuggled media.

North Korea has gone to extreme lengths to make sure its citizens can't casually access the foreign internet (or any internet).

For a time, according to Williams' report, foreign embassies in capital city Pyongyang ran open WiFi networks. Enterprising citizens with smartphones lingered nearby to browse the internet without being caught — until the state cottoned on and banned open networks.

Eventually, North Korea introduced its own public Mirae (Korean for "future") public network. It requires an app to use and, according to state media, only offers people access to North Korea's intranet and not the global internet.

North Korea doesn't have Netflix but, like much of the rest of the world, it is shifting to streaming TV.

According to Williams' report, there are two homegrown IPTV services, but the more popular one is called Manbang. Just like phones, the set-top box is built cheaply in China, imported, then reskinned as a domestically branded device.

People who own a Manbang device can stream a huge amount of state output, but can't tune into to foreign services. For now, people can also tune into traditional, over-the-air broadcasts (including foreign ones, if they have a hidden TV set). But, Williams concludes, North Korea could ban traditional broadcasts altogether and only put out content through IPTV.

This would make it even tougher for North Koreans to access foreign broadcasts.