A method for detecting fraudulent transactions entering a payment environment, the method comprising: receiving packets of a transaction from a network; reconstructing and framing the packets into respective transaction messages; decoding each transaction message into its respective fields; correlating the respective transaction messages into an end-to-end model of the transaction; applying one or more predefined rules to the respective fields to determine whether the transaction is fraudulent; when the transaction is determined to be fraudulent, determining one or more specified fields of the respective fields to use to selectively block, deny, or rate limit the transaction; selecting a corresponding predefined rule from a server rule base; storing the predefined rule in a transaction firewall rule base; and, applying the predefined rule to the transaction to selectively block, deny, or rate limit the transaction based on content of the one or more specified fields in the transaction.