The websites of both Nintendo and Epic Games have come under hacking attacks, causing them to issue warnings to registered users about password protection.
A warning remains on Nintendo's website, which underwent phishing attacks last week, reassuring customers that no financial information was compromised in the process. Parts of the website remain closed until the company feels that security has been re-established.
"We have learnt of a possible phishing threat to users of the European Nintendo website which we are currently investigating," reads a warning on Nintendo's UK site.
"The protection of our customers is our utmost priority and so we have taken the precaution of immediately shutting down some parts of this website until further notice. We would like to reassure you that we do not hold our customer's bank, credit card or address details on the European Nintendo website and so this data is not at risk.
"Phishing is when someone attempts to find out your personal information, such as usernames and passwords, by pretending to be a trustworthy person or company in an electronic communication such as an email or via a website.
"We apologise for any inconvenience this has caused. Please do get in touch with your local Nintendo Customer Services if you have any further concerns."
Epic's breach concerned the company's main website and forums, but the Unreal Engine developer doesn't hold any financial information on its customers. Nonetheless, an email was distributed to users warning them to change their passwords.
"Our Epic Games web sites and forums were recently hacked," read the mail. "After some downtime, they're back up and running now.
"The hackers may have obtained the email addresses and encrypted passwords of forum users. Plaintext passwords weren't revealed, but it's possible that those passwords could be obtained by a brute-force attack on the encrypted passwords. Therefore, we have reset all passwords. Your new password at the bottom of this message.
"The Unreal Developer Network (UDN) hasn't been compromised. Thankfully, none of our web sites ask for, or store, credit card information or other financial data.
"We're sorry for the inconvenience, and appreciate everyone's patience as we wrestle our servers back under control."
The attacks are the latest in a series of hacking attempts which seem to stem from the large scale assault which took Sony's PlayStation Network offline for six weeks prior to E3. Uk publisher Codemasters also had data stolen by hackers at the end of May, warning customers last week that "customer names and addresses, email addresses, telephone numbers, encrypted passwords and order history," had all been compromised.