Two US human rights charities have launched an appeal for donations of old USB sticks, also known as flash drives.

About 10,000 USB sticks are smuggled into North Korea each year by groups of people who have defected from the Communist state.

They are loaded with Hollywood films, South Korean TV shows and other material such as the Korean language version of Wikipedia.

In North Korea it is illegal content, and delivering it is dangerous.

In addition, the groups usually have to bear the cost of buying the flash drives themselves.

Most North Korean citizens have no access to the internet. Contact with the outside world is largely forbidden by the government, led by Kim Jong-Un.

"We really believe education is the solution in North Korea," Mr Gladstein told the BBC.

For many of us flash drives are becoming an obsolete technology - we have the cloud, and we can share things. But every single flash drive could save someone's life."

The Human Rights Foundation and Forum 280 are working with organisations such as the North Korean Strategy Center (NKSC), in Seoul, which distributes the sticks.

"It's always been a challenge to get people to understand why North Koreans' access to information is important, and this gives us a physical representation," Sharon Stratton, from the NKSC, told Wired.

"It's literally a key that will unlock a new world for North Koreans."

About 200 sticks have been sent in by individuals since the campaign's launch last week, and one has pledged to buy 10,000 for the appeal.

Mr Gladstein said he hoped corporations would donate unused branded drives ordered in bulk for corporate events.

Defectors describe increased demand for material from the outside world - and the preferred format has shifted from DVD to USB.

Arnold Schwarzenegger, Leonardo DiCaprio and Sylvestor Stallone are very popular," said Mr Gladstein.

US TV series Desperate Housewives and Spartacus and the Hunger Games films are also favourites.

Last year, Mr Gladstein was involved in a campaign that saw 10,000 copies of a 10-minute montage from The Interview airdropped into North Korea.

The film's fictional plot to kill Mr Kim outraged the government.

And the US believes North Korea was behind the subsequent hack of Sony Pictures, the studio behind the film.

North Korea has always denied the accusation.