Currently, we are receiving an increased number of contacts from users who are reporting that their accounts have been compromised. We have investigated the issue and have determined that unauthorised access has occurred in several cases. We are currently examining the cause of this issue. In each case the compromised account was accessed using the account holder’s correct password.
There is a possibility that some of the affected customers are using the same account names and passwords for their SQUARE ENIX account as other online services (belonging to other companies).

If you are using the same account name or password as your SQUARE ENIX account for another online service and that company’s information is compromised, there is a risk that a third party could gain access to your SQUARE ENIX account. Therefore, please do not use the same log in details as any other online service for your SQUARE ENIX account log in details.

In order to ensure account security, please keep the following in mind:

Do not use repeated strings of characters or information about you that can be easily discovered, such as phone numbers or birth dates, in your password.
Change your password regularly.
Do not use programs or websites that put you at risk of malware like PC viruses and spyware.
Do not open emails or attached files when you do not know who sent them.
Do not access suspicious websites.
Regularly Scan your PC for viruses, spyware and malware.

By using a SQUARE ENIX Security Token with your SQUARE ENIX account, you can greatly decrease the likelihood that your account will be compromised. We strongly recommend that you begin using one if you are not already doing so.

See the below URL for more information about Security Tokens.
http://account.square-enix.com/manual/en/about.html

In order to safeguard personal data, please ensure that you are using your account in a secure manner.