The two-year manhunt ended with the help of authorities in France and the United States, officials said. The investigation will examine whether the suspect had links to militants.
In a raid on the suspect's house in greater Athens on Monday, police seized computers, flares, shotgun cartridges, a homemade incendiary device, 130 fake credit cards, and €7,850 ($11,500) and $300 (€205) in cash hidden in a hollowed-out book, police said in a statement.
The suspect, who was not further identified, was arrested there on charges of computer fraud, forgery, illegal violation of privacy, and illegal weapons possession.
According to ekathimerini.com, the suspect was known online as "Splitter."
The website reported that the suspect had a tattoo on his back reading: "Capitalism is opportunity and opportunity is freedom."