Defensive Design

Defensive Design

1. Defensive design is when you anticipate all the ways a user can misuse a system or device.

   • When doing this you aim to stop misuse or the consequences of it.
     • It is unsuccessful when: - The program crashes -The program behaves in an unintended fashion -Data security has compromised

2. User Interface can often give the user too much freedom so you can't cover all the possibilities of them inputting the wrong thing so to begin you can try and make the user interface as simple as possible.

   • Menu driven interfaces are wuite good when you want to display a set of options to the user rather than letting them enter anything.
     • It is hard to just let the user input whatever they want so screen widgets can help limit their options. Certain 'graphics widgets' are useful, for example the calendar widget, the colour picker widget and drop down menus/spinners.
       • The purpose of widgets is to limit user choice to only valid values.

3. Normally, the easiest way to limit errors is to put detailed instructions of what to enter on screen.

   • We also use text entry the most but it is the cause of the most problems, but good instructions can change that.

4. Validation can be used in simple input boxes to check if what the user has entered is valid.

   • The four validation methods are: -checking and limiting the length of the data -checking the range of the data -checking the type of the data -checking the type of the data -checking the format of the data

5. A white list is a list of data that the application will accept as valid.

   • They are often used with firewall applications and email filtering applications. The firewalls can store URLs on the black list so it can warn you if they are dangerous, the same for emails.

6. A black list is a list of data that the application will reject.

   • It is easier to create a white list than a black list as it is easier to define what is acceptable than what is not.

7. Input sanitisation is when the data is checked before it is transferred. It is checked for leakage and is a form of data protection.

   • Encyrption is another form of defensive coding which makes sure that personal data is scrambled so that a hacker cannot read it without the key (which is stored elsewhere).