This document discusses various network security issues and methods. It covers topics like unauthorized access, malware, denial of service attacks, security methods like access rights and firewalls, and ways to protect against threats such as encryption, backups, and anti-virus software. Network security is important because when computers are connected, there are increased risks from other devices gaining access without permission. Hackers, viruses, and other threats can read or damage data if networks are not properly secured.

1. Chapter 13
Networks
anjan.mahanta@satreephuketipc.com
Cambridge A Level IT
13.02 Network security

2. 13.2 Network security
Security issues
When computers are connected together
through networks, there are increased security
risks due to access being available from other
computers.
2

3. Unauthorised access
● Commonly known as hacking, unauthorised access takes places when a
person or device gains access to a computer network without permission.
● Hackers can guess usernames and passwords to gain access to a network,
particularly when users set up weak passwords.
● Once hacker has access, they can read data on the system. This data may
be confidential to people or to the organization.
● The hacker may also make changes to the data, such as changing payment
details, or the hacker may destroy data deliberately to cause harm to the
organization or individual. 3

4. Malware
● Malware is a word used to describe any software
that is designed to cause damage.
● In relation to networks, the main problems are
viruses and spyware.
● Viruses copy themselves automatically to other
devices and so the connectivity of a network makes
the spread of viruses more likely.
● They are designed to cause damage to data or cause
problems to the operation of a computer system.
4

5. Malware
● Parasite viruses attach themselves to files on a
computer system and are triggered by certain
events such as date and time.
● Macro viruses attach themselves to macros that are
part of macro-enabled documents.
● Email viruses arrive as attachments to emails and
are triggered by the user opening the attachment.
● Unique to networks are worms which spreads
automatically through networks. Worms create
their own executable (.exe) files to spread.
https://www.youtube.com/watch?v=AfZxUK9U3hE
5

6. Malware
● Trojan horses are malicious programs that disguise themselves
as normal software, but if they are run they will actually cause
damage. https://www.youtube.com/watch?v=CvRIZHQMgco
● Trojans are often found on websites when a user tries to
download some illegal music or films and they end up download
a Trojan instead.
● Spyware is a software that secretly collects information without
the user being aware. It can log user activity including credit
card information or usernames and passwords.
● If a keylogger is used, then every keystroke made by a user is
recorded and this could include confidential data.
https://www.youtube.com/watch?v=kcoXJ6NhZ2U
6

7. Task
● Find out how the Blaster worm infected networked computers in 2003.
7

8. Denial of service attack
● A denial of service (DoS) attack is designed to send more requests to a server than it
can deal with.
● They are carried out to cause a disruption to an organization’s network or website
and often result in users not being able to use the network and customers not being
able to access the website.
● Website attacks are measured in requests per second (RPS) and it can only take
around 50 RPS to cripple a website.
● Network attacks are measured in gigabits per second (Gbps) and it can only take
around 20 Gbps of data to make a network unusable.
● DoS attacks are not designed to gain access to data, but purely to cause disruption.
A DoS attack could last for hours, days or weeks.
https://www.youtube.com/watch?v=DL1eQKkS2nI 8

9. Task
● Find out how the hacktivist group Anonymous used DoS attacks against ISIS
websites and social media in February 2015
https://foreignpolicy.com/2015/11/13/anonymous-hackers-islamic-state-isis-chan-online-war/
9

10. Security methods
Access rights
● When a user logs onto a network, they are given rights to access different parts of
that network. These access rights are usually related to data but can also be related
to services that are available, such as accessing the World Wide Web, accessing
email accounts and running software.
● The most common access rights that are given are:
○ Create C: users can create new items of data
○ Read R: users can read existing data
○ Update U: users can make changes to data
○ Delete D: users can delete data
10

11. Security methods
11

12. Task
● Research what makes a good password. Define set of rules for a password that is not
too restrictive on users but also ensures that the password is secure.
12

13. Choosing a password - the differences
between strong and weak passwords
There are programs available that are able to crack passwords and if a password is
short and contains just letters, then the password is weak and it is very easy to crack.
Many people use weak passwords because they find them easy to remember.
Here are some examples of weak passwords:
mypassword
Ahmed
Steve1234 13

14. Choosing a password - the differences
between strong and weak passwords
A strong password doesn't need to be long provided it contains symbols, capitals,
numbers, and letters. Although strong passwords are not impossible to crack, most
hackers would quickly move on to a different computer system where a weak
password had been used.
A strong password should be a combination of letters (capital and lowercase),
numbers, and symbols that have no relation to each other, just totally random such as
4Hp!9$R;
Here are some examples of strong passwords:
S%7c&X
£D23&!ul
14

15. Security measures
● Disable the user accounts at certain times of day so that the users who work from 9
a.m. to 5 p.m. can only access their accounts during that time and this prevents
someone from trying to use their account outside those hours.
● Security can also be put into place to ensure that certain user accounts can only be
accessed from specific computers.
● Two-factor authentication (2FA) can be used which requires two security
components to gain access. This can be simple as using a swipe card and a PIN but it
can also include more complex methods. Such as generating one time passwords
(OTP).
15

16. Task
16

17. Biometric methods
● Biometrics are biological characteristics that can be
measured.
● Biometric security uses these biological characteristics to
authenticate user’s identity.
● The biological characteristic has to be unique to each user
in order to be able to authenticate the user.
● Characteristics used for biometric security include:
○ Retina recognition
○ Facial recognition
○ Finger prints
○ Voice recognition
17

18. Firewalls
● Networks that have access to a WAN or internet have two-way traffic into and out of
the network.
● A firewall controls what data can flow into and out of the network.
● A firewall maybe a part of a router or it may be a software installed on a server that
sits between the gateway and the network.
● It is effectively a barrier between the network and external data traffic.
https://www.youtube.com/watch?v=kDEX1HXybrU 18

19. Firewalls
● Firewalls include an Access Control List (ACL) that uses a technique called
packet filtering.
● An ACL controls which packets are allowed through the firewall.
● The ACL will include a set of rules that determine which protocol, port
numbers, source addresses and destination addresses are allowed or not
allowed.
● If data packets are not allowed they will be dropped.
● For example, if the ACL includes a rule to block FTP, then all data packets for
port 21 (the FTP listening port) will be dropped. 19

20. Firewalls
20

21. Backup
● A backup is a copy of the original data. A backup is required if something goes
wrong and the original data is either damaged or lost.
● In the event of a problem with the data then the backup copy can be restored.
● A backup doesn’t stop a hacker from gaining access to data, nor does it stop
viruses from causing damage to data, but it is essential when recovering from an
attack.
● In a network, backup processes should be set to run automatically and regularly.
The more regularly a backup process is run, the more storage that will be required
for the backup data. 21

22. Backup
● Backing up data in cloud, which are effectively internet-based storage might be
beneficial which include not having to change tapes each day and the data being
away from the original in case of fire and flood.
● However, it also means that the data is connected and a part of a network which
could also suffer a security breach.
● Storing data on tapes means that the tapes have to be changed each day and then
relocated to a secure location away from the main servers.
22

23. Encryption
23

24. Encryption
● If information needs to be sent over the internet or another network and it needs
to be kept secure, then encryption should be used.
● Encryption scrambles the data while it is being sent and only the true recipient is
able to unscramble it. Should the data be intercepted by a hacker, then the data
will be totally meaningless.
● The process of scrambling data, sending it over the internet and then deciphering
it when it reaches the true recipient, is called encryption.
● This requires encryption and decryption keys.
24

25. Encryption should be used for:
● Sending credit card details such as credit card numbers, expiry dates, etc., over
the internet.
● Online banking.
● Sending payment details (bank details such as sort-code numbers, account
numbers, etc.).
● Confidential emails.
● Sending data between computers when confidentiality is essential.
25

26. Malware security
(anti-virus & anti-spyware)
● Anti-virus software now tends to be referred to as
anti-malware software as it deals with other threats, such
as adware and spyware, as well as viruses.
● It has two main functions:
● The first is an anti-virus monitor that is continually
monitoring the system for malware. If the anti-virus
monitor detects any unusual behaviour or tell-tale signs
of malware, then it will prevent that malware from being
executed so that it can’t cause damage to the files or
programs. 26

27. Malware security
(anti-virus & anti-spyware)
● The second function is to check for malware that may
already be on a system. This is usually known as scanning
the system.
● If any malware is found, then the user will be given the
option to disinfect the malware, put it into quarantine or
ignore it.
● Disinfecting the malware is the safest option as it
completely removes the malware from the system, but it
does mean that any data or program that included the
malware will be deleted. 27

28. Physical security methods
● Physical security methods are about protecting computer equipment. This can
include standard methods that are used to secure other equipment and buildings
or specialist physical devices that are designed to protect computer equipment.
● Security guards can be used to verify every person who enters a building or
specific rooms to endure that they are authorised to gain entry.
● Physical locks can be used on server room doors to prevent unauthorized access
to these rooms. These can be key locks, swipe card locks or numerical code locks.
● This kind of security should also be applied to back up tapes, which should be
stored in a safe that is kept off site.
28

29. Physical security methods
● Main servers should be protected against electrical
surges. This can be done using extension leads that
offer surge protection, but most servers will be
protected by uninterruptible power supply (UPS).
● UPS are basically battery packs that will provide power
in the event of a power cut, but will ensure that the
power supply is uniform.
29

30. Physical security methods
● Server rooms should be located in areas that are
protected from fires and floods.
● This should include providing additional fire protection,
such as a server room with fireproof doors, carbon
dioxide fire extinguishers and putting back up tapes in
fireproof safes.
● Server rooms should not be located in ground floor, which
can be susceptible to floods, and they should be away
from any water pipes that could potentially burst.
30

31. The principles of a typical data
protection act
The widespread use of ICT has made the processing and transfer of data much easier
and to protect the individual against the misuse of data, many countries have
introduced a law called a data protection act.
There are a number of problems in organisations holding personal data:
● The personal data might be wrong,which means wrong decisions could be made.
● The organisation may not take care of the personal data it holds so others may find
out about it.
31

32. 32

33. What exactly is personal data?
● Data about an identifiable person (i.e. the data must be about someone who can
be identified by name, address, etc.).
● Data about someone who is living.
● Data that is more personal than name and address. For example, medical
records, criminal record, credit history, religious or political beliefs, etc., are all
classed as personal data.
33

34. The effects of wrong personal data
● Your medical details could be
wrong, meaning you get the wrong
treatment - which could be life
threatening.
● Wrong decisions might be made;
for example, you could be refused
a loan.
● Wrong exam results could affect
you getting a job.
34

35. Rights of the data subject and the holder
● The person about whom the personal details are held is called the data subject.
● The person in the organisation who is responsible for the personal data held is
called the data holder.
● A data protection act is a law that protects individuals by placing obligations on
the organisations who collect and process the data (i.e. the data holders) in the
following ways:
35

36. Data Protection Principles
1. Personal data shall be processed fairly and lawfully.
2. Personal data shall be obtained only for one or more specified and lawful
purposes, and shall not be further processed in any manner incompatible with
that purpose or those purposes.
3. Personal data shall be adequate, relevant and not excessive in relation to the
purpose or purposes for which they are processed.
4. Personal data shall be accurate and, where necessary, kept up to date.
5. Personal data processed for any purpose or purposes shall not be kept for
longer than is necessary for that purpose or those purposes. 36

37. Data Protection Principles
6. Personal data shall be processed in accordance with the rights of data subjects
under this act
7. Appropriate technical and organisational measures shall be taken against
unauthorised or unlawful processing of personal data and against accidental loss or
destruction of or damage to personal data.
8. Personal data shall not be transferred to a country or territory unless that country
or territory ensures an adequate level of protection for the rights and freedoms of
data subjects in relation to the processing of personal data.
https://www.bbc.co.uk/bitesize/guides/z6kj6sg/revision/1
37

38. 38

39. 39

40. 40
DISCUSSION
● What kind of network do you have in your school?
● What possible security issues need to be considered?
● What does the school need to do to prevent these security issues from arising?
● What physical security methods does the school have in place?
● What logical (software based) security methods does the school have in place?
● What could the school introduce to make its network even safer?

41. 41