How To Void Getting Hacked in World of Warcraft

How does a Battle.net account become compromised?
Hackers will prey on your trust, naivety and innocence to discover your log-in credentials. Accounts become compromised when somebody discovers your log-in details (username & password) to the account.
Account Sharing
You share your account details with somebody you "trust". It's against Blizzard's Terms of Use to share your account details because it's so risky. Your friend could pass your log-in details to one of his friends, and so forth. Before you know it, everyone knows your account details. There is also no way of knowing if your friend has a secure computer; his computer might be infected by a Trojan/keylogger which means your account is then exposed. You might also fall out with your friend one day and he could decide to "get even" with you by stealing your gold and transferring to another realm.