No security is perfect.
The best you can do is try to remember not to hire crazy or untrustworthy people and then not to piss them off after you hire them. Segregate your really important data so that even if you have a general security breach, they still don?t have access to your very sensitive data and treat any employee who has access to the really sensitive data really well also run financial and security checks on them several times a year, and keep the number to less than 10 and no the CxO group is not part of that 10. Review and update your security model annually. Patch and update your own code every quarter or as vulnerabilities are discovered. Patch and update 3rd party systems within 30 days of them releasing a patch if not sooner.
But here is the thing. Sony knows how to run data security. They really do. But doing so it expensive and takes resources. Adding a second database layer so that the credit cards data isn?t stored with the rest of the data would probably have stopped them from being stolen, but it would have cost Sony extra money to setup and extra money to run. But If Sony really wanted to make data hacker proof or heavily hacker resistant. They could, and they very likely have. Lots of information they consider sensitive trade secrets that they don?t want to ever get out. For those they?ll spend the extra money. For your credit card they will not.