Correct Answer: A
Explanation/Reference:
Explanation:
A signature based IDS monitors packets and compares them against a database of signatures or attributes from known malicious threats.
Incorrect Answers:
B: An IDS which is anomaly based monitors network traffic and compares it against an established baseline, which identifies what is "normal" for that network, and the alerts the relevant party when traffic is detected which is significantly different to the baseline.
C: A statistical anomaly-based IDS is a behavioral-based system, which does not relies on a database of known attacks.
D: On-line network-based IDS monitors network traffic in real time and it analyses the Ethernet packet and applies it on the same rules to decide if it is an attack or not.
References:
https://en.wikipedia.org/wiki/Intrusion_detection_system
Harris, Shon, All In One CISSP Exam Guide, 6th Edition, McGraw-Hill, 2013, p. 258