I made a wrong transfer to an unknown blockchain account, how do I know who is that belongs to?
In general you cannot readily find out who owns an address.
If the owner of the address is especially careless, a great deal of detective work may allow their identity to be discovered eventually. This is not a trivial process.
I am very suspicious how people can transfer my btc out without my authorization.
They don't need your authorization, they only need to have once seen your private-keys. That gives them complete control for all time over any funds subsequently arriving at addresses associated with your private-keys.
As an example, many online-wallets (also called web-wallets or hosted-wallets) give control of your private keys to employees of the hosting service and to anyone who hacks that service. So any dishonest ex-employee might be able to empty your wallet. This sort of thing happens with depressing regularity.