A South Korean activist said Wednesday that he will launch balloons carrying DVDs of Sony's The Interview toward North Korea to try to break down a personality cult built around dictator Kim Jong-un.

The comedy depicting an assassination attempt on Kim is at the centre of tension between North Korea and the U.S., with Washington blaming Pyongyang for crippling hacking attacks on Sony Entertainment. Pyongyang denies that and has vowed to retaliate.

American security firm Norse cast doubt on the FBI's assertion that North Korea was behind the attack. In a company blog post earlier this week, the firm suggested that there is evidence that disgruntled former employees "may have joined forces with pro-piracy hacktivists" to "to infiltrate the company’s networks."

Unusual movie premiere

Activist Park Sang-hak said he will start dropping 100,000 DVDs and USBs with the movie by balloon in North Korea as early as late January. Park, a North Korean defector, said he's partnering with the U.S.-based non-profit Human Rights Foundation, which is financing the making of the DVDs and USB memory sticks of the movie with Korean subtitles.

South Korean activists, like this group seen in 2012, frequently launch balloons containing leaflets denouncing Kim Jong-un towards North Korea. (Kim Hong-Ji/Reuters) Park said foundation officials plan to visit South Korea around Jan. 20 to hand over the DVDs and USBs, and that he and the officials will then try to float the first batch of the balloons if weather conditions allow.

"North Korea's absolute leadership will crumble if the idolization of leader Kim breaks down," Park said by telephone.

If carried out, the move was expected to enrage North Korea, which expressed anger over the movie. In October, the country opened fire at giant balloons carrying anti-Pyongyang propaganda leaflets floated across the border by South Korean activists, triggering an exchange of gunfire with South Korean troops.

Plan has problems

But it is not clear how effective the plan will be, as only a small number of ordinary North Korean citizens are believed to own computers or DVD players. Many North Koreans would not probably risk watching the movie as they know they would get into trouble if caught. Owning a computer requires permission from the government and costs as much as three months' salary for the average worker, according to South Korean analysts.

The movie, starring James Franco, left, and Seth Rogen angered the North over its depiction of the leader's assassination. (Columbia Pictures/Sony/Ed Araquel/Associated Press) Not everyone supports sending balloons into the North, with liberals and border town residents in South Korea urging the activists to stop. North Korea has long demanded that South Korea stop the activists, but Seoul refuses, citing freedom of speech.

Park said the ballooning will be done clandestinely, with the pace picking up in March when he expects the wind direction to become more favourable.

Calls to the Human Rights Foundation on Wednesday were not immediately answered. The foundation says on its website that it works with North Korean defectors to use hydrogen balloons to send material across the border, as well as smuggling items through China and broadcasting radio transmissions to reach those who own illegal short wave radios.