Hi, all:

I develop a bitcoin trading platform, that include one online wallet.

I think that all users be able to withdraw cash in any time, so I don't use
any offline wallet. I call my online wallet is "pure hot wallet" :-)

I will set password in online wallet, only I know the password, and will
create 100000+ users, every user will have at least one transaction of
recharge bitcoin and withdraw cash.

I have two question now:
1. If nobody can get file "wallet.dat", does my wallet is security?
2. If somebody can get the file wallet.dat, does he or she can get all the bitcoin?

Thank you.