Unit 4: Network Security Edexcel GCSE Computer Science

LAN

A network of computers covering a small geographical area located on a single site

WAN

Covers a large geographical area connecting LANs. Uses 3rd party infrastructure (BT cables, etc). (The internet is an example of this.)

MAC address

Media Access Control: Each unique piece of hardware on a network has this type of address.

Packet Switching

A method of transferring data by breaking it into small chunks called packets.

Server

A computer that holds data to be shared with other computers (A web server stores and shares websites)

WWW

World Wide Web: All the interlinked HTML pages that can be accessed over the Internet

The internet

Global communication network that allows computers to connect and exchange information

Firewall

Network security system that checks incoming and outgoing data, using a set of rules, deciding whether to allow the data from entering or leaving the network

Hacking

The act of gaining unauthorised access to a computer system and its data

Malware

Malicious software - intended to harm or disrupt a computer system

Protocols

sets of rules that networks rely on to allow different devices to communicate with each other

Baiting

Persuading victims with something desirable, such as a free download, to trick them into downloading malware.

Phishing

When attackers trick individuals into revealing sensitive information by posing as trustworthy entities via email or messages.

Quid pro quo

Offering a service or benefit in exchange for sensitive information (e.g. promising IT assistance in return for login credentials.)

Pretexting

Attackers create a fake scenario to gain someone's trust and extract sensitive information (e.g. pretending to be a coworker to obtain company data)

Social engineering

Hackers use their social skills to trick people into revealing access credentials or other valuable information

Access control

In security terms, the process of determining and assigning privileges to various resources and data.

Penetration testing

simulating hacking the system by attempting to find and exploit vulnerabilities (without causing harm)

White box pen testing

Tester has perfect knowledge of the system, the insider's perspective

Black box pen testing

The tester knows nothing about the systems under attack - outsiders perspective

Biometric authentication

Uses personal physical characteristics such as fingerprints, facial features, and retinal scans to authenticate users

Examples of Physical security

CCTV cameras

Security guards

Door locks

Password policies

Ensures passwords meet minimum requirements and are changed regularly.

Ransomware

Software that encrypts programs and data until a ransom is paid to remove it.

Data integrity

The correctness of data after processing, storage or transmission.

Denial of service

An availability attack, to consume resources to the point of exhaustion

Backup and recovery procedures

Critical data and files can be retrieved if they become lost or corrupt. Backups can be set up to be automatic, based on a schedule, manual, incremental or full.

Ethical hacking

When an expert is employed to penetrate a computer system in order to find security vulnerabilities

Authentication

A method for confirming users' identities

Principle of Least Privilege

A security discipline that requires that a user, system, or application be given no more privilege than necessary to perform its function or job.

File permissions

The use of user and file attributes that control which users can read, write, move, or delete each file.

Encryption

Process of converting readable data into unreadable characters to prevent unauthorized access.

Multi-factor authentication (MFA)

A type of authentication that requires more than just a password for account access. Involves two or more of the types of authentication (something you know - password, etc, something about you - fingerprint, etc, something you have - keycard, etc)

Advantages of networking

users can share files

users can share peripherals

users can access their files from any computer on the network

Disadvantages to networking

increased security risks to data

malware and viruses can spread easily between computers

if a server fails, connected computers may not work

How is data sent across a network?

Data is split up into packets for transmission
The header of each packet contains a source and destination IP

It also contains a sequence ID, which means packets can be reassembled into the correct order

Range

The maximum distance a transmission can travel before becoming degraded.

Latency

The time it takes between a transmission being sent and recieved.

Bandwidth

The maximum amount of data that can be transferred per second.

Wired network aspects

More reliable and secure

Transfer data at faster speeds

Require additional cabling

Wireless network aspects

No need for physical connection

Less reliable

Lower transfer speeds

Speed

The transfer rate of data from a source to a destination (measured in bits per second)

Ethernet

Family of related protocols providing the basics of communication over a LAN

Wi-Fi

Family of related protocols for wireless communication

Protocols for communication over LANs and WANs

TCP (Transmission Control Protocol) - provides an error free transmission between two routers

IP (Internet Protocol) - Routes packets across a WAN

Webpage protocols

HTTP (Hypertext Transfer Protocol) - A client-sever method of requesting and delivering HTML web pages

HTTPS - Encryption and authentication for requesting and delivering HTML web pages

Email protocols

STMP (Simple Mail Transfer Protocol) - Sends an email to the mail server and from one mail server to another mail server

POP3 (Post office protocol v3) - downloads the mail and deletes it off the server

IMAP (Internet Message Access Protocol) - used to download email from the mail server

File transfer protocol (FTP)

transfers files between the FTP client and FTP servers

Advantages of layering

Reduces complexity of a problem into sub-problems

Devices can be manufactured to operate at a specific layer

What protocol operates at the Application layer?

(any one from) FTP, HTTP, HTTPS, STMP, POP3 IMAP

What protocol operates at the Transport layer?

TCP

What protocol operates at the Internet layer?

IP

What protocol operates at the Link layer?

Ethernet or Wi-Fi

What is the function of the application layer?

the appropriate protocol is selected based on which application is running (e.g. email client, web client (browser), FTP client)

What is the function of the transport layer?

• When sending, data is split up into packets, a sequence number and checksum is added to the header of each packet

• When receiving, reassembles packets in the correct order using their sequence numbers and requests for missing packets to be resent

• overall, TCP establishes a connection between devices and ensures that is sent without errors

What is the function of the Internet layer (IP protocol) / router ?

1. looks at the destination IP address of the packet

2. uses a routing table to decide which router to forward the packet to

3. sends the packet to the chosen next router

• overall, packets are sent from source to destination through the fastest pathway possible

What is the function of the Link layer?

sends one packet a time from one node (device, router) to the next

Advantages of a Star topology

If one connection fails, all other devices will continue to operate

It is easy to add new devices without disrupting the network

Disadvantages of a star topology

If the central switch fails, the entire network will shut down

Requires a lot of cabling, which can be expensive

Advantages of a mesh topology

new devices can be added without interruption or interfering with other devices

messages should always get through as they have many possible routes on which to travel

Disadvantages of a mesh topology

overall cost is high because much more cable is required

many connections require a lot of maintenance

Advantages of bus topology

Easy to set up

Relatively cheap to install because little cabling is needed

Disadvantages of bus topology

The whole network will fail if a terminator is removed

if the main cable fails, the whole network will fail

System vulnerabilities caused by people

Not installing latest OS updates

Not keeping anti-malware up to date

Not logging off computers

Describe how a checksum is used to identify packets that have been corrupted

• A checksum formula is applied to the packet before it leaves the source computer

• At the receiving end, the same checksum formula is reapplied

• The new checksum is compared to the received checksum in the packet header

• If the checksums do not match, a resend request is sent

White hat hacker

a person assigned to try and hack a server in attempt to find vulnerabilities so they can be fixed

Methods of protecting networks

Firewalls

Physical security

Access control

What is access control

Used to control permissions in users and files

Levels of access control

read only

read/write

execute

full access (can edit access levels of other users)