Depends on whether it had any Bitcoins in it first of all (empty wallet won't get the hacker anything), second is the password (if set) and third is the phrase that can be used if password needs to be reset based on the forgotten password attribute. Though the wallet file contains all the information from having the private key(s) of your address (es) and all their transactions, it's next to impossible to decrypt those private keys and the only way to steal everything is to know the password - so setting up a strong password is the key to save your coins from being stolen.