Sony is to appeal a 250,000 fine issued by the Information Commissioner's Office (ICO), which was levied against the firm as punishment for the 2011 hack on its online Playstation Network.
The Japanese electronics firm's Playstation Network was taken offline by hackers in April 2011, compromising the names, addresses, and account details of more than 77 million of the site's users.
The ICO claim the breach was avoidable, as Sony could have done more to protect users' payment card and log-in details through software updates.
David Smith, deputy commissioner and director of data protection at the ICO, said the case is one of the most serious breaches the data protection watchdog has ever dealt with.
"When the database was targeted albeit in a determined criminal attack the security measures in place were simply not good enough," said Smith.
Sony Computer Entertainment Europe strongly disagrees with the ICO's ruling and is planning an appeal.
"There's no disguising that this is a business that should have known better...[as] it trades on its technical expertise, and there's no doubt in my mind that they had access to both the technical knowledge and resources to keep this information safe," he added.
In a statement to IT Pro, Sony said it "strongly disagrees" with the ICO's ruling and is planning to appeal.
This, the company said, is in light of an acknowledgement by the ICO that there was no evidence that encrypted payment card details were accessed or that any of the compromised data was used for fraudulent purposes.
"Criminal attacks on electronic networks are a real and growing aspect of 21st century life and Sony continually works to strengthen our systems, building in multiple layers of defence and working to make our networks safe, secure and resilient," the statement continued.
"The reliability of our network services and the security of our consumers' information are of the utmost importance to us, and we are appreciative that our network services are used by even more people around the world today than at the time of the criminal attack."
Get the ITPro. daily newsletter
Receive our latest news, industry updates, featured resources and more. Sign up today to receive our FREE report on AI cyber crime & security - newly updated for 2023.