I think both the new and old casinos try as much as they can to protect their customers' data, but then again, we should all be aware that immediately we submit our document online for KYC verification, it's now out there, and we should be prepared for the worst. Any casino can be hacked, both old and new ones, and the older ones are even more of a target for hackers than the new casinos.
Right, if we passed our personal information to the casinos, they we indeed trusted them to handled it very carefully. Nevertheless, we should think for the worst, what if our personal data has been leaked, maybe they were hacked and our information was stolen? That could be the worst case scenario. So even if it is a established casino, they are not safe from this hackers. That's why they really have the big responsibility to handle our sensitive information and knows how to protect it as it could ruined their reputation once they've been hacked.