Your firm is the auditor of Motor Components Ltd, which manufactures electrical components it then sells to car manufacturers and retailers. It has a number of factories, at different geographical locations, which manufacture the components, and all accounting information is kept on a mainframe computer at the head office. Access to the computer is through terminals at the head office and the factories. The factories use the national telephone system to transmit information to, and retrieve information from, the computer at head office.

You have been asked by the partner in charge of the audit to consider the controls that should be used to permit only authorised input and retrieval of data from the main computer by staff at head office and at the factories.

Required

(a) Describe the controls that can be used to control access to the main computer from terminals at head office and consider the effectiveness of each of them.

(b) Consider the controls that should be instigated in addition to those described in (a)
above to prevent unauthorised access to the computer through the national telephone system.