Mostly the account-theft becomes noticeable, when the malefactor has already caused the damage. Below are given actions that he is capable to perform after hacking your account:

• to kill your character again and again till it looses all its belongings and experience points
• to perform unlawful actions on behalf of your character
• to hand over character’s belongings and money to other player’s
• to ask other players to lend some items or money on your behalf
• delete your characters

As you see, malefactor’s actions can cause not only a material damage, but also can influence negatively on your game reputation.