1.3 Prohibit direct public access between the Internet and any system component in the cardholder data environment

1.3 Examine firewall and router configurations—including but not limited to the choke router at the Internet, the DMZ router and firewall, the DMZ cardholder segment, the perimeter router, and the internal cardholder network segment—and perform the following to determine that there is no direct access between the Internet and system components in the internal cardholder network segment:

While there may be legitimate reasons for untrusted connections to be permitted to DMZ systems (e.g., to allow public access to a web server), such connections should never be granted to systems in the internal network. A firewall’s intent is to manage and control all connections between public systems and internal systems, especially those that store, process or transmit cardholder data. If direct access is allowed between public systems and the CDE, the protections offered by the firewall are bypassed, and system components storing cardholder data may be exposed to compromise.