The man, whose identity has not been released, is accused of infecting computers in Spain and South America, primarily Chile and Peru, with the Tasin worm. He is also believed to have launched an attack against his home city Ejica's official website.
According to El Mundo, one of the variants, Tasin.C, picked up national interest when it was discovered that it downloaded photos of famous pin-up girl Nuria Bermudez to entice victims to open emails containing the worm.
A Civil Guard official said the investigations began in November, when an antivirus company was first alerted to the outbreak. Reports suggest that the worm's author worked from university computers and his home PC.