Problem:
(a) What is a firewall and which are its most important tasks?
(b) What is the difference between default deny and default permit? Which advantages and disadvantages do the two strategies have? (c) Many companies implement one or more firewalls between their "internal" network and the external Internet. Explain, using a diagram, a typical firewall-based Internet connection, and explain briefly the purpose and likely configuration of each of the components.
(d) What is the role of an intrusion detection system (IDS) in a network? Explain the operation of a signature based IDS. Discuss its advantages and disadvantages.