A heuristic intrusion detection system (IDS) provides the most protection against emerging threats, as it uses behavioral analysis and anomaly detection to identify unknown or zero-day attacks. A heuristic IDS can adapt to changing patterns and learn from previous incidents, making it more effective than a signature-based IDS, which relies on predefined rules and signatures to detect known attacks. A demilitarized zone (DMZ) is a network segment that separates the internal network from the external network, and it can provide some protection against external threats, but not against internal or emerging threats. Real-time updating of antivirus software is important to protect against malware, but it may not be sufficient to prevent new or sophisticated attacks that exploit unknown vulnerabilities. References: CISA Review Manual (Digital Version) 1, page 452-453.