11.1 List and briefly define three classes of intruders. 11.2 What are two common techniques used to protect a password file? 11.3 What are three benefits that can be provided by an intrusion detection system? 11.4 What is the difference between statistical anomaly detection and rule-based intrusion detection? 11.5 What metrics are useful for profile-based intrusion detection? 11.6 What is the difference between rule-based anomaly detection and rule-based penetration identification? 11.7 What is a honeypot? 11.8 What is a salt in the context of UNIX password management? 11.9 List and briefly define four techniques used to avoid guessable passwords.