3.1 Defensive Desgin

Question 1

What are the things you must consider when creating a program that is secure and robust

Answer 1

. Anticipating Misuse
. Input Sanitization
. Validation
. Verification
. Authentication
. Maintainable Code

Question 2

Anticipating Misuse

Answer 2

Planning ahead to take steps against potential misuse (e.g Twitter preventing the same tweet sent twice in a row).

Question 3

Input Sanitisation

Answer 3

Cleaning up data that has been input, (e.g. removing special characters to prevent a SQL injection).

Question 4

Validation

Answer 4

Checking whether input data follows criteria and should be accepted. (e.g. length check on a password).

Question 5

Verification

Answer 5

Checking whether data has been entered correctly (e.g. double entry).

Question 6

Authentication

Answer 6

Ensuring only authorised users can gain access to a system (e.g. passwords)

Question 7

Maintainable Code

Answer 7

Allowing other programmers to understand the code (e.g. comments, indentation, meaningful variable names).

Question 8

What is validation

Answer 8

Validation is a process to check that data is reasonable or sensible before it is accepted.

Question 9

What is a Range Check

Answer 9

Checks data is within a certain range.

Question 10

What is a Type Check

Answer 10

Checks data is a certain data type.

Question 11

What is a Format Check

Answer 11

Checks data is entered in a certain way.

Question 12

What is a Presence Check

Answer 12

Checks that data has actually been entered and not left blank.

Question 13

What is a Lookup Table

Answer 13

A table of acceptable entries, also known as a list.

Question 14

What is a Length Check

Answer 14

Checks the length of the input is within a certain amount.

Question 15

How should Programs be written

Answer 15

Programs should be written in a way that makes maintaining and understanding them as straightforward as possible.

Question 16

What are examples of making a program maintainable:

Answer 16

.Using subprograms to reuse code and make them easier to test. This is called modularization

.Appropriate variable names, using a naming convention, ensure the purpose of a variable is immediately understood

.Using indentation to improve readability and clearly show each ‘block’ of code.

.Comments enable a programmer to understand the purpose of each line of code. Crucial when working in a team.

Using constants is another method of improving maintainability. This keeps the program code consistent, which makes it easier to read and debug a program.