Security specialist Sophos has put out a stark warning to anyone who has entered their credit card details on the PlayStation network, saying they should "cancel that card immediately".
Sony this week admitted that a hacker has infiltrated the PSN and, along with it, the personal information of potentially all of the 70 million people who use the service.
In the UK, three million people are part of the PSN, and Graham Cluely from Sophos believes that everybody should be changing passwords and cancelling cards to minimise any damage.
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"If you're a user of Sony's PlayStation Network, now isn't the time to sit back on your sofa and do nothing," said Cluely.
"The fraudsters won't wait around - for them this is a treasure trove ripe for exploiting. You need to act now to minimise the chances that your identity and bank account become casualties following this hack."
"That means, changing your online passwords (especially if you use the same password on other sites), and considering whether it would be prudent to inform your bank that as far as you're concerned your credit card is now compromised."
Alongside credit cards and passwords, there were also personal details obtained – such as dates of birth, email account information, names and addresses.
Christopher Boyd, senior threat researcher at GFI Software, is also worried about the implications of the data breach.
He explained: "The breach is extremely serious, but the key question is whether or not the person or group responsible was able to obtain the details of all 77 million PSN users or only 'some' of them.
"What's particularly frustrating for users of the PSN is that anybody unsure of what information is stored against their account such as personal information, card details and password reset answers won't know until the service is back online.
"It's crucial that access is restored as soon as possible so that users can confirm what information might have been compromised."
Sony does not yet know how systemic the hack was, but announcing that all credit card details could be compromised means that this could be one of the biggest data leaks the web has ever seen.