Homework 4 – Software Engineering – CSCI 362-001

11.4 – Giving reasons for your answer, suggest which dependability attributes are likely to be most critical for the following systems:

An Internet server provided by an ISP with thousands of customers – Availability and reliability so that the thousands of customers can get the services they pay for.

A computer-controlled scalpel used in keyhole surgery – Safety, reliability, and security so that when the scalpel does perform, it does so correctly and does not cause damage. Security is involved in this so that the system is not compromised and used to murder patients.

A directional control system used in satellite launch vehicle – Availability, reliability, and security are paramount. This is so that the satellite can be moved out of the way of debris at any time without worrying about malfunctions, and security so that it isn't used for terrorist purposes.

An Internet-based personal finance management system – Security and reliability are the most important. The finances should not be compromised at any cost, and accidents involving the finances should not occur.

11.7 – In a medical system that is designed to deliver radiation to treat tumors, suggest one hazard that may arise and propose one software feature that may be used to ensure that the identified hazard does not result in an accident.

An example of a hazard in this situation is that the sensor that measure how much radiation is to be released may stop working. In this situation the software should not allow the treatment to proceed until it is fixed.

11.9 – Using the MHC-PMS as an example, identify three threats to this system (in addition to the threat shown in Figure 11.8). Suggest controls that might be put in place to reduce the chances of a successful attack based on these threats.

An unauthorized user will gain access to the system by infecting an access terminal and stealing login credentials.

An unauthorized user will harass and clog the system in an attempt to cause a denial of service.

An unauthorized user will bypass login terminals and inject malicious software into servers in order to change or steal confidential information.