SEOUL - South Korean police said Friday they have arrested a hacker for staging cyber attacks similar to those that crippled domestic and US websites this week.

The 39-year-old identified only as Choi is accused of paralysing the homepage of the government Game Rating Board by using a distributed denial-of-service (DDoS) method.

Choi was an agent for software developers seeking approval from the board for new games. Because he failed to finish one job on time, he crashed the site to create an excuse for his tardiness.

Choi is accused of buying a hacking programme from an ethnic Korean in China. Using a server in Shanghai and mobilising some 7,400 "hijacked" computers, he allegedly crippled the ratings board site 10 times between March 4 and 22.

He has not been implicated in this week's DDoS attacks but the case illustrated the relative ease with which they can be mounted.

Hackers plant viruses in the personal computers of thousands of unsuspecting people. These generate a huge volume of simultaneous requests for access to selected websites, causing them to freeze up.

South Korea's spy agency has raised suspicions that the North or its sympathisers were behind the cyber attacks this week that shut down US and South Korean government and private websites.

US experts were divided on whether the communist state was likely to blame for the attacks, which highlighted the vulnerabilities of the Internet.