Usually only after they have obtained a money judgment and a writ of execution from an official. In California, you get the judgment first then the writ of execution to attach the accounts, then the sheriff's office serves the writ on the bank. If you were to try and hide your bank account information from creditors, the creditor can force you to tell them by dragging you into court under an order of examination process. If you lie to the creditor and they find out after you've completed the order of examination, you can be held in contempt and jailed for up to 6 months in county jail.