Abuse & Misuse Cases

Overview

The purpose of this activity is to get you acquainted with writing abuse and misuse cases in tandem with writing use cases.

Setup

This activity is for groups of 4-6 people. Your instructor will assign each team a different system. For this exercise, your team is in charge of coming up with the system's functionality, as well as specifying the requirements. Please assign the following roles:

• Scribe - the person who is writing the use case document
• Customer - the person who determines the functionality of the system

Activity

1. (3 minutes)Give your system a title. Start up a document on GoogleDocs (make sure it has edit sharing permissions with the instructor), call it "Requirements Specification for X" where X is will title of your system. Also, place the following headers in the document to be filled out:
   • Overview
     • Description
     • Actors
     • Security Goals
   • Use Cases
     • Primary Actor
     • Preconditions
     • Main Flow of Events
     • [Misuse|Abuse] Case
   • Security Requirements
2. (10 minutes) Conduct a requirements elicitation session with the customer. Document the main features of the system. The customer is in charge of brainstorming the functionality, but must be reasonable as the instructor can override any customer decision. The scribe takes informal notes from this meeting (no requirements just yet).
3. (10 minutes) Elaborate on the requirements by outlining three use cases and filling in the Overview section. What is the system, in general? What are the general security goals of the system? Who are the actors (both regular and malicious)? Write the titles of three use cases, and define the relevant actors for each use case. Don't write the scenarios just yet.
4. (10 minutes) Write the main flow for one use case. Make this about 4-10 steps. Be specific about what information is being exchanged. You may add alternative flows if you see the need, but they are not required for this exercise.
5. (10 minutes) Now write either a misuse case or abuse case (your choice) for that use case. A few notes:
   • Be sure to include both flow of events and harm done.
   • Make sure the flow affects your main flow, not your preconditions. You may violate a precondition in the process, but this section is for demonstrating how you can abuse/misuse the main flow.
   • Update the header to label each one as either Abuse or Misuse.
6. (15 minutes) Write your other two use cases, and an abuse or misuse case for each. Thus, your requirements document should have at least one abuse case and at least one misuse case, and three in total.
7. (10 minutes) Now that you have defined multiple different abuse and misuse cases, generalize those into security requirements that are not specific to any particular use-case, but are specific to your system. Document it this way:
   • Add a list to the end of your requirements document that defines these security requirements. Each security requirement should have a self-documenting identifier, e.g. "Sec1"
   • Add security requirement references to the step in the primary flows (and alternative flows if you added any).
8. (15-20 minutes) Be ready to discuss your use cases with the rest of the class. We will spend about 3-5 minutes on each team.

Submission & Grading

This activity is worth 10 points, and your grade is based on in-class participation. Nothing is due beyond class today, as long as you are participating and are reasonably close to completion. Your instructor will check your GoogleDoc before the end of class.