2.3.1 Defensive Design

Why does defensive design need to exist?

• To stop people breaking stuff

• To protect programs from being punched in the face

• To punish computer misuse

• To protect programs from being misused by users

How is this programming being misused?

• entering numbers into name

• entering letters into name

• entering symbols into name

• entering cake into name

How is this programming being misused?

• Entering letters into age

• Entering numbers into age

• entering symbols into age

• entering an invalid range

How is this programming being misused?

• Entering letters into properties

• Entering numbers into properties

• Entering a number that is too small

• Entering an invalid range into properties

What could be used to prevent this?

• Whipping people that do this

• Input validation

• Input sanitisation

• Input verification

What's a black list?

• A list which is black

• A list of data not allowed into a program

• A list of data allowed into a program

• A list of data not allowed into a club/pub

What should NOT be in the black list for the field "name?"

• Numbers

• Symbols

• Text

• entries over 20 characters long

What's happened here?

• User has a fat face - input errors

• User has fat fingers - inputting data

• User has a fat face - inputting data

• User has fat fingers - input errors

What has happened to make the data okay again?

• Validation

• Clean up

• Verification

• Sanitization

What should have happened here before the user had access to this data?

• Authentication

• PIN

• Password

• A username