I'm not sure about an automatic rule for incoming messages, but you can filter your inbox to show only messages with blank "To" and "Cc" fields.
To set the custom filter go to the View tab, click View Settings, click the Filter... button, and then the Advanced tab in the dialogue box shown in the screenshot below.
To pick out the messages you receive by way of BCC, click the Field drop-down menu, go to Frequently-used fields, and select To. Set the condition to is empty, and click Add to List. Do the same for the CC field and click OK.