We have been defrauded many times by the same person, under different names and billing addresses. However, he consistently uses the same shipping address. How can we block some address or postal codes so we don’t get defrauded again?
Perhaps you can try this fraud prevention module as it is free, easy to set up and provides validation rules customization to block addresses or postal codes for your case to prevent fraud orders.
Most of these have ongoing costs (must be indicated as per magento marketplace terms and conditions in the description)... but there is at least this one Fraud Prevention M2 by Plugin Company that "does not involve any additional service costs or periodical subscription fees") I think is closest to your needs.