Five banks, three airlines, two telecommunication firms and one insurance company were all hit by the hacker who disrupted their websites and online payment systems.
The unnamed teenager has confessed to Norway's biggest ever cyber-attack on businesses. He was arrested on Thursday morning and questioned by police in Bergen.
Police chief, Frode Karlsen, said to the newspaper Bergens Tidende: "[The youth] is charged for causing malicious damage, but the charge could be extended. The maximum penalty for such a crime is six years."
Police do not suspect that the hacker operated in cahoots with an organized group. Karlsen said: "He could have had help, but we don’t think that he is a part of an organized group. We do not have any proof of this right now."
The teenager contacted the police on Tuesday and claimed he was part of an activist group who were behind the cyber-attack.
Defence lawyer, Christian Børve, said to Bergens Tidende: "He is sorry for having caused this situation and my client has admitted his guilt."
Police worked with Norway's National Criminal Investigation Service to track down the hacker.
The hacking attack is one out of 16 serious incidents so far this year targeted at private and public companies in Norway, according to NorCERT, the national centre for handling serious hacking attacks against society's critical infrastructure and information in Norway. 51 cyber-attacks were recorded in 2013.
Norges Bank, DNB, Sparebank 1, Nordea, Danske Bank, Storebrand, Telenor, NetCom, Norwegian, Widerøe and SAS were all affected by the attack.