In order for your bank account to be garnished by a creditor, the creditor must obtain a judgment against you and go through the judicial process to garnish your account. If they do have a judgment, they can freeze your account. However, you are entitled to claim certain funds exempt before they are allowed a garnishment (and you have to pay attention to any notices sent to you). If you receive a notice that your account has been garnished it is up to you to claim an exemption on any of the funds. If you are unsure what to do, you should contact an attorney and/or legal aid organization as soon as possible.
It is up to you to claim the exemption. Be prepared to send copies of Statements to support your claim.
If the deposit is made by direct deposit, the bank probably put the creditor's attorney on notice of the exempt status of some, if not all, of the funds.