11.4 Use intrusion-detection and/or intrusion-prevention techniques to detect and/or prevent intrusions into the network. Monitor all traffic at the perimeter of the cardholder data environment as well as at critical points in the cardholder data environment, and alert personnel to suspected compromises.
Keep all intrusion-detection and prevention engines, baselines, and signatures up to date.
11.4.a Examine system configurations and network diagrams to verify that techniques (such as intrusion-detection systems and/or intrusion-prevention systems) are in place to monitor all traffic:
• At the perimeter of the cardholder data environment
• At critical points in the cardholder data environment.
11.4.b Examine system configurations and interview responsible personnel to confirm intrusion-detection and/or intrusion-prevention techniques alert personnel of suspected compromises.
11.4.c Examine IDS/IPS configurations and vendor documentation to verify intrusion-detection and/or intrusion- prevention techniques are configured, maintained, and updated per vendor instructions to ensure optimal protection.
Intrusion detection and/or intrusion prevention techniques (such as IDS/IPS) compare the traffic coming into the network with known “signatures” and/or behaviors of thousands of compromise types (hacker tools, Trojans, and other malware), and send alerts and/or stop the attempt as it happens. Without a proactive approach to unauthorized activity detection, attacks on (or misuse of) computer resources could go unnoticed in real time. Security alerts generated by these techniques should be monitored so that the attempted intrusions can be stopped.