Network Security

ways a user can keep their home PC secure:

Back up your data – this stores your data somewhere safe so the hacker or virus cannot get to it.

Stay away from rogue websites – websites that seem fake, such as without an unsecured web link and if they have poor layouts

Avoid adverts that sound fake – such as adverts offering “a million dollars” this will probably be a scam to try and steal your personal information

Don’t reveal your personal information to unsafe websites – like if you’re about to buy something from a website that does not seem secure they might steal your card details and such.

Avoid opening unknown emails – these unknown emails may lead to a link that lets a virus into your computer.

3 additional methods to having a secure computer

Always update your computer so it has the best working security software to protect your computer even more.

make sure your passwords aren’t too easy to guess, make them complex and that only you can understand them.

Use a firewall..

What is a firewall and how does it work?

it is a system designed to prevent unauthorized access of other users/hackers/viruses

the firewall has two network interfaces: one for the external side of the network, one for the internal side.

firewalls can block traffic intended for particular IP addresses or server ports.

Explain the difference between a hardware and a software firewall


Firewall Software which protects individual PC users from malware and hacking attacks, can be downloaded from trusted security companies and are easily accessible

A hardware firewall uses a PC-like appliance to run software that blocks unwanted outside traffic

What is encryption?

the process of converting information or data into a code, especially to prevent unauthorised access. Prevents unauthorised access to a user’s computer.

Explain how encryption works by use of a key

Keys allow a user to encrypt data to hide it from others, and then decrypt it in order to access the original.

What is a proxy server? – it is a software that is a gateway between a computer and local network.

it is safe because you are transferring all your data to another location, which means no viruse or hacker can access your data.


Denial of service attacks

A denial of service attack is an attack that makes a user lose access to their data.

One of the attack was on the paypal website, it prevents some of their customers in certain regions from accessing and paying through paypal. it was not attacked directly and nothing important about that website was disrupted. there were just some minor problems

Another one of the attacks was on a company called Dyn, it is a website that stores user’s global address books and keep them up to date, basically it is a company where firms are responsible for forwarding large volumes of internet traffic. When the attack happened the same that happened to paypal had happened to Dyn. Users lost access to their data, and the targets were bombarded with junk traffic. the attacks were coming from millions of addresses, which made it one of the worlds largest attacks.

The company cannot prevent this from happening by blocking the attacks because then they would be blocking of main website such as google or openDNS. The only way they could prevent was that they should have multiple vendors for core services like routing internet traffic, and they should also have many security experts to prevent this from happening in the future.

link to news page –


Error Detection & Correction

Type Description Example Use
Check Digit The last digit of a sequence used to check all other digits are correct and in the correct order  ISBN number
ARQ Used to check that data has been successfully sent by waiting for an acknowledgement of receipt Global system for communication
Checksum A calculated total of other data sent used to detect changes in bits during transmission Calculator
Parity Check Used to make the total number of 1s sent either even or odd ASC11

Odd Parity – 01001010, 11010011

Even Parity – 11011011, 10101010

Situations that parity checks could fail? – if any two digits are changed rather than just one.



Networking and the Internet

What is a network? 

A network is a connection of different computers all linked together, it can be a small connection such as within a building or school, then there are big connections such as the internet.


the advantages are: you’re able to share files, share internet connections and devices, and you can communicate as well, and you can access the files anywhere anytime.


you cannot rely much on open network connections, information can be lost or stolen. the cost of sharing an internet connection or a network connection can cost a lot of money. there is also a risk of viruses and hacking that could happen, especially connections that aren’t protected.

What hardware would you need to set up a network?

you need: routers, hubs, bridges, and switches


are used to connect devices in one single form of hardware, in one single building, offices use these and so do we in our daily homes.

hubs, bridges and switches

allow other devices to connect to the router for a shared connection.

What is a server?

a server is a connection that shares and provides information.

What is the internet?

The internet is a worldwide network, that any computers can join. it is a series of LANS – which is a local area network, that means the internet is made up of many small connections which all connect into one big network.

What do you need to connect to the internet? 

a computer, a router, a search engine

all of the things above are needed to connect to the internet.

What happens when you try to access a particular website?

the address is sent to the main server, then the IP address is the address used to access this particular website.

Term Definition
Network  A network is a connection of many different computers
LAN  It is a local area network, used in schools, offices.
WAN  Wide area network, such as the internet is worldwide.
Data Transmission  sending information over physical connections
ISP  Internet service provider, a provider that sells internet such as BT WiFi
MAC Address  is a network address that makes every network unique and easily identified
IP Address  A unique string of numbers to easily identify different computers
URL  the address of the worldwide web, Uniform Resource Locator
HTTP  The Hyper Text Transfer Protocol, is the foundation of data communication
HTTPS  encrypts and decrypts users pages, and is used in front of every website.


A Browser is a program used on a device to navigate to, access & display web pages.

Name 5 browsers commonly used.

Google Chrome, Firefox, Internet explorer, Opera, Chromium

Look at two browsers and make a list of
a) Their similarities – features they both share

Google Chrome – search bar is in the middle of screen, has logo above search bar, also traditional search bar at the top of the screen.

Firefox – also has the search bar in the middle of the screen, and the traditional search bar at the top
b) Their differences

Google Chrome – is slightly more faster more advanced the results of searches load up faster, whereas Mozilla Firefox is slower and the actual website itself is a little duller than google chrome.

Browsers are often responsible for caching and administrating cookies.

What is a ‘web cache’ and why is it used? – information technology for temporary storage

What is a ‘cookie’ and why is it used? – small piece of data sent from a website and stored on the user’s computer by the user’s web browser while the user is browsing

One function that Browsers can provide is file transfer, using File Transfer Protocol (FTP)

What is a protocol? – a set of rules the website follows

Why is a protocol needed for file transfer? –   FTP is used to transfer files between computers on a network. because some restrictions and regulations need to be set in order to transfer files.

Give two examples of situations when someone may want to use their browser for file transfer.


CMS – stands for Content management system, it is a set of related programs that are used to create content, this means that the HTML code has already been made and it up the user to input in any information to fill in the code. it is typically used for enterprise purposes to design webpages that are viewed by the public eye.

Advantages –

It is a faster development, Ability to add or edit pages on your website yourself, Useful in organisations, with many content contributors, that perhaps need to audit additions and changes to content being made.

Disadvantages –

Using a CMS effectively can require certain computer skills that you or your staff may not have. such as sometimes not knowing the program that helps you make the page can be quite confusing. Can require extra maintenance, backups, upgrades, security patches.



HTML – stands for Hypertext markup language, a system to create webpages that can be altered such as the font alignment and text color can be adjusted and designed to your preference. Every webpage is a HTML file that has been altered to support the webpages setting and information.

HTML tags are the hidden keywords within a web page that define how your web browser must format and display the content.

An HTML element is an individual component of an HTML document or web page, once this has been parsed into the Document Object Model.