Department of Computer Science and Technology

Course pages 2018–19

Software and Security Engineering

Principal lecturer: Dr Alastair Beresford
Taken by: Part IA CST 50%, Part IA CST 75%
Past exam questions

No. of lectures: 11
Suggested hours of supervisions: 3
This course is a prerequisite for the Group Project.


This course aims to introduce students to software and security engineering, and in particular to the problems of building large systems, safety-critical systems and systems that must withstand attack by capable opponents. Case histories of failure are used to illustrate what can go wrong, and current software and security engineering practice is studied as a guide to how failures can be avoided.


  • What is a security policy or a safety case? Definitions and examples; one-way flows for both confidentiality and safety properties; separation of duties. Top-down and bottom-up analysis methods. What architecture can do, versus benefits of decoupling policy from mechanism.

  • Predicting user behaviour. Predicting and mitigating user errors. The hierarchy of harms. Attitudes to risk: expected utility, prospect theory, framing, status quo bias, gender. The characteristics of human memory; forgetting passwords versus guessing them.

  • Security protocols; how to enforce policy using cryptography and structured human interaction. Man-in-the-middle attacks. The role of verification and its limitations.

  • Bugs of different types: design errors, implementation errors affecting arithmetic, logic, syntax, and concurrency. Code injection attacks. Defensive programming: secure coding, contracts. Fuzzing.

  • The software crisis. Examples of large-scale project failure, such as the London Ambulance Service system and the NHS National Programme for IT. Intrinsic difficulties with complex software.

  • The software life cycle. The software life cycle. Getting the specification right; requirements analysis methods; modular design; the role of prototyping; the waterfall and spiral models.

  • Designing for Testability. Identifying different types of tests and how to use them effectively. Writing a good unit test; understanding techniques for measuring test quality.

  • Modern development practice and quality assurance. Tools to support code management, code review and test case generation. Continuous integration, refactoring, release engineering, patch strategies. The need for code indexing, code ownership, library management, design documentation and the maintenance of safety and security ratings.

  • Software-as-a-Service. The Software-as-a-Service architecture, including a/b testing, phased release of client and server components and rearchitecting systems while in operation.

  • Critical systems: where real-time performance, safety or security is essential. Examples of catastrophic failure; problems with usability and human error for both safety engineering and security engineering.

  • Real-world challenges in combining safety and security. Project planning tools; PERT and GANTT charts. Open source: advantages and drawbacks. Evaluation and assurance; maintaining a security rating or a safety case.


At the end of the course students should know how writing programs with tough assurance targets, in large teams, or both, differs from the programming exercises they have engaged in so far. They should understand the different models of software development described in the course as well as the value of various development and management tools. They should understand the development life cycle and its basic economics. They should understand the various types of bugs, vulnerabilities and hazards, how to find them, and how to avoid introducing them. Finally, they should be prepared for the organizational aspects of their Part IB group project.

Recommended reading

Howard, M. & LeBlanc, D. (2003). Writing secure code. Microsoft Press.
Anderson, R. (2008). Security engineering (Part 1 and Chapters 25-26). Wiley. Available at:
Leveson, N. (1994). Safeware. Addison-Wesley.

Further reading:

Brooks, F.P. (1975). The mythical man month. Addison-Wesley.
Reason, J. (2008). The human contribution. Ashgate Publishing.
Maguire, S. (1993). Writing solid code. Microsoft Press. Report of the inquiry into the London Ambulance Service (SW Thames RHA, 40 Eastbourne Terrace, London W2 3QR, February 1993).