The attack has severely affected users of Telia's online services with many struggling to get a steady connection on Friday.
"It started just after 1 o'clock and seems to be the same kind of attack as before," Henrik Johansson of Telia told the TT news agency.
David Jacoby, chief researcher at data security firm Kaspersky Lab said the attack likely stems from a police raid earlier this week against the file-sharing Pirate Bay in Stockholm.
Swedish cops briefly ground the site with its Swedish domain name before it come online again a few hours later with a different domain name.
According to Jacoby the group that claims to be behind the Telia attack, Lizard Squad, is one of many underground groups involved in the anonymous Pirate Bay movement.
"These attacks don't come from nowhere. The Pirate Bay raid has provoked feelings in these groups," Jacoby told the TT news agency.
He added; "There will most likely be more similar attacks against film companies, games companies and public authorities," he said.
Twitter has already closed two accounts linked to the Lizard Squad in the wake of the attack.
A previous attack over Tuesday and Wednesday also caused headaches for the company. A Telia spokesman told The Local at the time that the company had put "technical arrangements in place to ensure [an attack] won't happen again".
Lateon Thursday, a well known hacking collective called Lizard Squad claimed responsibility for the attacks. It is understood that Lizard Squad was targeting gaming company Electronic Arts, which uses Telia for net connection.
The group has a long history of carrying out DDOS attacks, which entails a website being bombarded with communication requests so that the servers become overloaded and the site crashes.
The group has targeted XBox Live and the Playstation Network in the past, and even tweeted out a bomb threat to a plane carrying a Sony executive.
Over five million Swedes use Telia to provide their home phones, TV and mobile services. The company is part-owned by the Swedish state.