Defensive Design

Defensive Design

1. Helps to insure programs function properly

   • When functioning properly they should never break and never produce errors

2. Programmers try to protect their programs through defensive design.

   • Anticipate how users might misuse their program, then attempt to prevent it from happening.
   • Ensure their code is well-maintained.
   • Reduce the number of errors in the code through testing.

3. Input Sanitisation

   • removing any unwanted characters before passing data through the program.
     • Programs can use a mixture of input sanitisation and validation to verify that the inputted data has an acceptable format before passing it into the program

4. Input validation

   • checking if data meets certain criteria before passing it into the program. E.g. checking that an email address contains an @ symbol and has a suitable ending (.com, .co.uk,etc).
     • sanitisation and validation are often done using whitelists and blacklists. Whitelists tend to be more secure, however they can take a long time to set up and can be too restrictive

5. Whitelist

   • A whitelist is a list of all data that a program should accept - any data that isn't on the whitelist will be rejected.

6. Blacklist

   • A blacklist is a list of all the data that a program should reject- any data that isn't on the blacklist will be accepted.

7. Authentication can help protect programs.

   • can confirm identity
   • Passwords need to be changed every 6 weeks

8. program should be easy to maintain.