Sven Olaf Kamphuis is accused of launching a distributed denial-of-service attack on Spamhaus, a non-profit organization that detects spam email at its source and blocks it, ThinkSpain reported Sunday.
Kamphuis, 35, is reported to be the manager of Cyberbunker and organizer of the group Stophaus.
Authorities said he traveled all over Spain in a van equipped with antennas that allowed him to stage the attacks without being tracked.
Maria Buyo, a representative of the National Police in Barcelona, said authorities in the Netherlands had begun investigating the cyberattack after huge amounts of data were sent to the anti-spam site in an attempt to shut it down.
Buyo said the cyberattack slowed the Internet around the world.
Authorities alleged that Kamphuis staged the attack because Spamhaus had blocked a number of servers hosted by Cyberbunker.
Kamphuis told the media that Spamhaus "did not have the right" to choose "what should and should not" be on the Web.