@shasan, if I can remember correctly then in the past someone [may be more members] suggested you to ask for signed message from the borrowers. I hope you are practicing it in your business.
- Reused password.
No one is hack proof but reusing password deserves to be hacked or you will not learn lessons.
If anything happen to an account and the account takes any loan then the original account holder is responsible for it. There are no escape.