While giving examples, give key differences between Discretionary access control and mandatory acccess control [4 Marks] 

(b) Human element is an important consideration in any security issue because it contributes heavily to realization of attacks primarily because a human attacker is behind the development of an attack tool and will still be the one to run the first attack command. Describe FIVE phases of the hacking methodology [10 Marks]

 (c) Briefly describe the challenge handshake authentication protocol (CHAP) [6 Marks] Question FOUR [20 Marks] 

(a) Explain and with the support of a diagram how you can use public key cryptography to encrypt and distribute/share public key [10 Marks] (b) Explain and with the support of a diagram how you can combine public key cryptography and hash functions to create a digital signature [10 Marks] COMP 424 Page 3 of 3 Question FIVE [20 Marks] 

(a) Illustrate using a diagram a basic security model that can be used to protect networks [8 Marks] 

(b) Briefly describe the first THREE steps of security risk assessment in an organization that has invested heavily in computer based systems [6 Marks] 

(c) Describe while giving examples THREE types of controls that can be used to manage security risks in an organization