Data Representation and Cyber Security

Question 1

State the decimal representation of the binary number 10010100

Answer 1

148

Question 2

State the hexadecimal representation of the binary number 10010100

Answer 2

94

Question 3

State the hexadecimal representation of the decimal number 143

Answer 3

8F

Question 4

State the binary representation of the hexadecimal number BE

Answer 4

B - 1011
E - 1110
10111110

Question 5

Give two reasons why hexadecimal is often used instead of binary in computer science.

Answer 5

Hexadecimal is easier for humans to read than binary

It is quicker to type in hexadecimal than binary

Question 6

what is the answer to 01010101 + 01101100 + 00011001

Answer 6

11011010

Question 7

State the result in binary of performing binary shift 2 places to the left on the value 00111001

Answer 7

11100100

Question 8

What is the largest decimal number that can be represented using 6 bits

Answer 8

63

Question 9

How many bits are there in 5kb

Answer 9

5000
* 8
* 1000
40,000

Question 10

Explain how a sound wave is converted so that it can be stored in a computer.

Answer 10

A microphone or sound sensor picks up the sound wave
The wave is converted from an analogue to digital signals
The height of the wave is measured
the sample are stored as binary values.

Question 11

A student has recorded a 30 second digital sound track using a sample rate of 44 000Hz. 8 bit have been used to store each sample taken.
Calculate the file size in kb.

Answer 11

44,000 * 8 * 30 = 10,560,000
10,560,000 / 8 = 1320000
1320000/1000 = 1320 kB

Question 12

What is data compression

Answer 12

C- the process of encoding information to try and use fewer bits than the original

Question 13

Give 2 reasons why data compression is often used.

Answer 13

To speed up file transfer

To use less storage

Question 14

RLE is one method of compressing data

State the feature of data that allows it to be compressed effectively using RLE

Answer 14

The data contains lots of runs

Question 15

Describe how RLE works. Give an example

Answer 15

It looks for consecutive repeating data in a file - called a run. Instead of storing each pice of repeated data separately, it stores the number of times it repeats.
An example is a image of how the specific rows of pixels would be compressed

Question 16

Define the term cyber security

Answer 16

Cyber security aims to protect networks, data, programs and computers against damage, cyber attacks and unauthorised access

Question 17

Define the term malware.

Answer 17

Malware is malicious code that is designed to cause harm or gain unauthorised access to a computer system

Question 18

What is the definition of social engineering

Answer 18

C - the art of manipulating people so they give up confidential information

Question 19

Phishing is a form of social engineering.

Describe 2 methods a school could use to protect its staff and students from phishing

Answer 19

Tell staff and students to not click on files or attachments from unknown senders
Train staff and students to never enter personal information in a pop up screen

Question 20

Explain how each of the following cyber security threats could be used by a student to gain unauthorised access to a school network

• weak passwords
• misconfigured access rights
• removable media
• unpatched/outdated software

Answer 20

Weak passwords, students code use brute force methods. Default passwords can be published online so everyone knows them
Misconfigured access rights
Allows students to access areas they are not supposed to , students can reconfigure network.
Removable media
Could contain malware that allows students to gain access, can be used to steal data
Outdated sofatware
Could allow students to exploit known weakness
A student can install malware.

Question 21

What are the sizes/units used to store data

Answer 21

Bit - 1 or 0
Nibble - 4 bits 
Byte - 8 bits
Kb - 1000 bytes
MB - 1000 kilobytes
GB - 1000 megabytes 
TB - 1000 gigabytes

Question 22

What are the base numbers for binary

Answer 22

1,2,4,8,16,32,64,128

Question 23

What happens in binary shift , multiplying

Answer 23

It shifts to the left, the number is doubled

Question 24

What happens in binary shift, divding

Answer 24

It shifts to the right, the number is halved

Question 25

What are the bases of hexadecimal

Answer 25

1,16,256,4096

Question 26

What are character sets

Answer 26

Collections of characters that a computer recognises from their binary representation.

Question 27

What is ASCII?

Answer 27

Each character has 7 bit binary code

represents 128 different characters

Question 28

What is the difference between ASCII and Unicode

Answer 28

Unicode comes in several different forms and tries to cover every possible letter or symbol. It has multiple bytes for each character.
All major languages is covered.

Question 29

What are the type of images usually found?

Answer 29

Bitmap . Bitmap images are made up of pixels.
The colour of each pixel is represented by binary code
Black and white images use 2 colours so need 1 bit.

Question 30

What is image resolution ?

Answer 30

the number of pixels in an image. The more pixels , the better quart of image but also more file size.

Question 31

What affects the size and quality of sound files.

Answer 31

• Sample rate , how many samples you take in a second
  Same resolution - number of bits available
  However increasing this increases file size too.

Question 32

What are the two types of compression?

Answer 32

Lossy and Lossless

Question 33

What is lossy compression and what are the pros and cons of it.

Answer 33

Lossy compressions works by permanently removing data from the file. 
Pro - reduces file size, 
Less bandwidth 
Cons - loses data 
Can't be used on text or software files 
Worse quart than original 

e.g. MP3

Question 34

What is lossless compression and what are the pros and cons of it.

Answer 34

Lossless compression makes the file smaller by temporarily removing data to store the file and then restores it to its original state.
Pro - data removed temporality
can be used on texts and files
Turned back to original
con - only slight reduction in file size

E.g. PNG

Question 35

What is penetration testing ?

Answer 35

Penetration testing is when organisations employ specialists to stimulate potential attacks to their system. It is to identify possible weaknesses in their cyber security.

Question 36

Compare white box and black box penetration?

Answer 36

White box penetration tells a malicious insider who has knowledge on the system to identify weaknesses. They are given user credentials.

Black box penetration stimulates an external cyber attack. The person is not given any credentials and try to hack in any way they can.

Question 37

Describe 3 different categories of malware.

Answer 37

Worms - like viruses but self replicate without any user help, meaning they can spread very quickly. They exploit weaknesses in network security.
Trojans - malware disguised as legitimate software. Trojans do not self replicate - users install them not realising they have a hidden purpose.
Spyware - Secretly tracks actions like key presses and sends info to the hacker, who might be able to work out things like passwords and bank details.

Question 38

What is pharming

Answer 38

User is directed to fake version of a website
Asks for personal information
Can be prevented by up to date anti malware software and web filters.

Question 39

Images can be represented in a computer’s memory as a bitmap. Explain how an image can be represented as a bitmap.

Answer 39

Image is divided into pixels
Each possible colour is represented by a (unique) bit pattern
The colour of each pixel is stored
The order of the bit patterns for the individual pixels indicates where the pixel will appear in the image

Question 40

Define sampling rate.

Answer 40

number of samples taken per second;

Question 41

Explain each of these security measures:
Authentication
Encryption

Answer 41

Authentication is ensuring that a user is who they are
claiming to be, e.g.. password, fingerprint
Encryption is changing data so that it cannot be read (except by authorised users)