The 35-year-old Dutch citizen was arrested in Spain in April, and he is believed to be behind the biggest DDoS attack in the history of the Internet aimed at international spam-tracking outfit Spamhaus.
Kamphuis was arrested in his home in the city of Granollers near Barcelona, which functioned as a communication center, and has apparently been circling Spain in a van equipped with computer equipment, routers, antennae and has been using it as a mobile office.
In a recent interview he said to be the spokesman for Stophaus, a group of organizations that actively works against Spamhaus, which has flagged them all as spammers and has obviously damaged their functioning. Still, he says that he is not a member, and claims that Chinese and Russian members of Stophaus are behind the attack.
The NYT reports that he has not been charged, but is going to be kept in custody for the next 14 days while the Dutch Police's High Tech Crime Team continues their investigation into the attack. When this period passes, a court will decide whether he will be free to go or will be kept in custody - again, without being charged - for up to 90 days.
In the meantime, some Dutch government and business websites - including the Dutch DigiD e-signature system - have been hit by DDoS attacks, and some of them are purportedly executed by Kamphuis' supporters as revenge for his arrest and incentive for his release.