Which of the following monitors network traffic in real time? 

Answer options:

A. network-based IDS
B. host-based IDS
C. application-based IDS
D. firewall-based IDS

A

This type of IDS is called a network-based IDS because monitors network traffic in real time. Source: KRUTZ, Ronald L. & VINES, Russel
D., The CISSP Prep Guide: Mastering the Ten Domains of Computer Security, 2001, John Wiley & Sons, Page 48.