11.5.1 IDS/IPS monitoring of CDE traffic

Network intrusions must be detected and/or prevented, using IDS and/or IPS techniques, in such a way that: all traffic at the CDE perimeter is monitored; all traffic at critical points inside the CDE is monitored; personnel receive alerts about suspected compromises; and every detection and prevention engine, baseline and signature is kept up to date. Guidance (definition): critical points can include network security controls between segments (for instance between a DMZ and the internal network, or between networks inside and outside scope) and points guarding connections from less trusted to more trusted components. Objective under the customized approach: mechanisms that detect suspicious or anomalous network traffic in real time, which may point to threat actor activity, are in place, and their alerts are acted on by staff or by automated responses that prevent system components being compromised by the detected activity.

Source: PCI DSS v4.0.1, 11.5.1. The statement above is our statement of the clause, read from the published text and cited so you can check it against the official text, not the instrument verbatim. Open PCI DSS v4.0.1 in the compliance library.

Version 4.0.1 is the active version; 4.0 has been retired. Appendix A1 applies only to multi-tenant service providers, A2 only to card-present POS POI terminals that still use SSL or early TLS, and A3 only when a payment brand or acquirer requires it. Which requirements apply to you follows your validation type.