Dutchman 'planned biggest ever cyber attack from bunker near Barcelona' He is believed to be behind the March 15 cyber attack on Spamhaus, a non-profit Swiss-based company that fights internet spam by blocking emails offering products such as discounted Viagra or weight-loss pills. Mr Kamphuis, who publicly branded the service as censorship after some of his own email addresses were blacklisted, was being investigated by Dutch authorities as the mastermind behind so-called "distributed denial-of-service" (DDoS) attacks. DDoS attacks overwhelm a server with traffic, jamming it with incoming messages. The attack against Spamhaus was the most powerful to date and threatened to collapse the global internet. It was described by the Netherlands National Prosecution Office as an "unprecedentedly serious attack" deemed three times more powerful that other recent cyber-attacks against US banking sites. Mr Kamphuis was detained on a European Arrest Warrant following cooperation between Dutch, German, British, US and Spanish police and on Monday was remanded to prison by a judge in Barcelona pending extradition to the Netherlands. Police seized two laptops and a variety of different equipment thought to have been used for criminal activity.