A hacker who stopped more than three million Spanish computer users from using the internet has been sentenced to two years in jail. Twenty-six-year-old Santiago Garrido used a computer worm to launch distributed denial-of-service (DDoS) attacks after he was expelled from the popular "Hispano" IRC chat room for disobeying its rules.

The attacks disrupted an estimated three million users of the Wanadoo, ONO, Lleida Net and other internet service providers - amounting to one third of all of Spain's web users at the time of the 2003 offense.

Garrido, who went by the aliases "Ronnie" and "Mike25," was sentenced at a court in La Coruña and also faces a 1.4 million Euro fine.

"Many times hackers use DDoS techniques to try and blackmail the website under attack. On this occasion, it seems the hacker was so furious about being thrown out of a chat room that he resorted to a criminal act to wreak his revenge, affecting millions of internet users in the process," said Graham Cluley, senior technology consultant for Sophos. "This type of activity causes serious damage and disruption, and any hackers engaged in such behaviour must be punished accordingly. The Spanish Civil Guard should be congratulated for seeing this case through to its conclusion."

SophosLabs estimates that more than 60 percent of all spam originates from zombie computers, which can be used by criminal hackers to launch DDoS attacks, spread unwanted email messages or steal confidential information. In May 2005, the Sober-Q trojan and Sober-N worm were found to have worked in tandem to infect and hijack computers around the world, programming them to spew out German nationalistic spam during an election.