The unidentified teenager, who reportedly lives with his mother in Agios Dimitrios, a district of Athens, had originally broken into the Interpol site when he was just 15 years old.
"He has carried out such strikes all over the world from his home," the head of Greece's cybercrime squad Manolis Sfakianakis is quoted as saying on NET, the Greek state TV station.
"Interpol is the basic one, and government sites in the US. He acted alone, though he has worked with others before", he said.
Sfakianakis added that the young hacker - using an alias if 'nsplitter' - also stole credit card and e-banking data through toolbars downloaded by internet users, and generated cloned cards to make unauthorised ATM withdrawals.
Overnight reports suggest that the hacker has been released by Greek police pending further investigation.
The AFP newswire, says that, during his arrest on Wednesday, police executed a search warrant on his home and seized almost 8,000 euros, $300, laptops, external drives and a router.
According to the Softpedia newswire, the teenager had 130 blank cards which he wrote with stolen credit card data in order to perform fraudulent cash withdrawals.
"He used part of the illegally obtained funds to invest in almost 50 companies listed on the Athens stock exchange", says the newswire.
"If found guilty of all charges, he faces a prison sentence of at least five years", the newswire adds.