Three South Koreans have been indicted on charges for buying hacking programs from North Korean agents that were used for Pyongyang's cyber attack against Seoul last year, prosecutors said Wednesday.

The three suspects, whose names are withheld, allegedly bought remote-controlled surveillance programs to spy on other people's cards when gambling for 14 million won (US$13,700) from hackers working for North Korea's cyber warfare unit in China in 2011.

They spread the software in South Korea through peer-to-peer (P2P) sites in the hopes of raising interest in the product and then selling it to online gambling site operators, according to the prosecution.

Prosecutors said that North Korea used the programs to stage the latest March 20 attack, targeting South Korea's TV stations and financial companies, as the software also helped hackers break into personal computers and collect private data.

"The suspects were aware of the danger and risk of the North Korean programs that can steal data and be used for cyber attacks," said one of the investigators.

"And North Korea sells hacking programs and uses them for denial of service (DDoS) attacks against the South." (Yonhap)