Network Security

Ways to keep home PC Secure

  1. Install Firewall- A firewall takes on the roll of a security guard. There are two firewall types, A Software Firewall and a Hardware Firewall. The job of a firewall is to create a barrier between your computer and any unauthorized programs or data packets trying to come through the internet.
  2. Install Antivirus Software- Antivirus is a means to protect your computer. This software helps protect your computer from unauthorized code or software which could pose as a threat to the system.
  3. Install Anti-Spyware Software- Spyware is a software program that can collect personal information about any organization without needing approval. The info then goes to a third party website.
  4. Use Complex and Secure Passwords- It is very important to have complex passwords since hackers would take much longer to figure out your password.
  5. Check on the Security Settings of the Browser- Browsers have various security settings and privacy settings which you should look at and set to the level of safety that you desire. Recent browsers are giving you the ability to make websites not be able to track your movements, which would increase privacy and security.

 Three Methods of Security

The three other methods of security are to log after using a device. By doing this, it will prevent someone from accessing your computer without knowing your password. You can also keep your files stored somewhere safely, which would not allow them to access and use your files. Lastly, you can use authorized personnel, and this only allows certain people to access your laptop, and prevents unknown people to use your PC.


Firewalls can be used to check data packets to make sure that they have been received by a computer system from a network or the internet. They also check packets, and if a packet does not get accepted, it cannot pass through the firewall.

The difference between a hardware firewall and a software firewall is that the hardware firewall protects the entire system, whereas the software firewall protects a single computer, and is much cheaper.


Encryption- when data has been converted into a code. Encryption stops unauthorized access.

Encryption Key- A key used to encrypt data, but not the same key used for decryption of the data.

What is a proxy server?

Proxy Server- A computer that is used as a gateway between local network, servers provide increased performance and improve security.

Proxy Server can keep data safe since it is improving the performance along with having more secure access.

NHS Cyber Attacks

Some countries became attacked by a cyber gang known as the shadow brokers. Japan, Russia, UK, US, and South Korea and computers in various countries became hacked. The hackers used a malware that went into the computer after it’s user opens an unknown email or page on which the virus has been stored. As soon as the malware is on the computer, the computer is locked, forcing the user to pay money to regain control or they would lose all of their files. After this, the user will get the decrypt code. The malware that arrives on your computer is very hard to stop. The FBI has also decided that it would be best to just pay the ransom they have demanded. It cannot only happen to global companies or government agencies, but can also occur to you. The simplest way to avoid having these problems is by not opening suspicious pages and update your laptop regularly.

Denial of Service Attacks (DDOS)

A distributed denial-of-service (DDoS) is an attack in which multiple systems are flooding the bandwidth or the resources in the system that is targeted. This is normally one or more web browsers. An attack such as this one will cause multiple systems to be compromised. The targeted system gets flooded with lot’s of traffic. The traffic that arises is coming from many different sources instead of one source. It will make it very effective and shall make the attack very difficult to stop. For example, Google is trying to prevent this from happening by creating a multi layer defense system. It will also give you access to journalist, human rights, news and elections monitoring sites even if it happens to get attacked. It is impossible to prevent it from occurring. Amazon is also providing an AWS shield which will also add more layers of protection.




A browser is a program that is used on a device to navigate to, access and display web pages.

Name 5 Browsers commonly used.

  • Google Chrome
  • Internet Explorer
  • Safari
  • Mozilla Firefox
  • Tor

Look at two browsers and make a list of- Google Chrome and Internet Explorer

a) Their similarities- features they both share

The similarities of both of these web browsers have very simplistic designs, both are simply used and accessed easily, and they both also have search bars on the top.

b) Their differences

These two web browsers can be very similar, but Google Chrome can load pages very quickly, and has much more for a student or work life. Internet Explorer does work better on Windows. However, this is not as useful as Google Chrome Browsers. Google Chrome browsers are often very responsible for caching and administrating cookies.

What is a web cache and why is it used?t

What is a cookie and why is it used?wand tracks what website you are going on.

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

What is a protocol?

A protocol are a set of rules for transmitting data between electronic devices, such as computers.

Why is a protocol needed for file transfer?

Protocols are needed for file transfer so that nothing that is not allowed on the rules can be transmitted onto the computer. And so that it is not a jumbled mess of data that is being sent to the computer.

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





Error Detection and 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  Barcodes
 Automatic Repeat Request (ARQ) Used to check that data has been successfully sent by waiting for an acknowledgement of receipt  Email Account Confirmation
Checksum A calculated total of other data sent used to detect changes in bits during transmission  Used for Downloading Installation File
 Parity Check Used to make the total number of 1s sent either even or odd  Checking Odd Paritys

Parity Check

A parity check uses a parity bit to make sure that the data has been sent accurately. Data is sent in bytes, normally made up of 8 bits. In a parity check, the first 7 bits of the byte are the data itself, the last bit is the parity bit.

Odd Parity



Even Parity



In what situation could Parity Checks fail?

If you send two sets of data at once, the Parity Check will fail.




A Network is created when more than one device has been combined together. A network can also be known as a small collection of computers that are connected within a building (EX: School, Home or Business) or a wide collection of computers that are around the world.

Networking Advantages

  • Communication- it is easy and often free to communicate using email, text messages, voice calls and video calls
  • Roaming- if information is stored on a network, it means users are not fixed to one place. They can use computers anywhere in the world to access their information.
  • Sharing Information- It is easy to share files and information over a network. Music and video files, for instance, can be stored on one device that can be shared across many computers, so every computer does not need to fill hard drives with files.
  • Sharing Resources- it is easy to share resources such as printers. Twenty computers in a room could share one printer over an entire network.
  • Sharing Software- it is possible to stream software using these web applications. This is avoiding the need to download and store the whole software file.

Networking Disadvantages

  • Dependence- users that are relying on a network might be stuck without having much access to it
  • Hacking- Many criminal hackers will try to break into the networks to gain personal information and peoples banking details. This is not possible on a stand-alone computer without having to break into the room, but is much easier with a network.
  • Hardware- routers, network cards and other network hardware is required to set up a network. At home, this is very easy to set up a wireless network without technical expertise. However, a very complicated network in a school or an office would require professional expertise.
  • Viruses- networks make it easier to share viruses and other malware. They can quickly spread and damage files on many computers via a network.

Network Hardware

Network Interface Card (NIC)- Any computer that is to be connected to a network. It needs to have an NIC. Many modern computers will already have the NIC built into the motherboard, but some computers may require an extra expansion card (small circuitboard).

Network Cable- In order to connect many different devices to create a network, cables are required. Many cables are still used in most networks, rather than using the wireless, since they can carry a lot more data per second, and this ensures that it is more secure (less open to hacking).

Hub- A device that can connect to a number of computers to create a LAN. The hub is mainly used at the centre of a start network, or part of a hybrid network. The hub has many cables plugged in from every computer.

Switch- This is similar to a hub since it also connects many computers to create a LAN. The switch is also used at the centre of a star network, or part of a hybrid network. This will also contain cables plugged in from each computer. Switches are much more intelligent than Hubs since they check message addresses and send it to that specific computer. This is much more secure than the Hubs, but will make it slightly more expensive.

Router- It is a network device that connects together two or more networks. A very common use of the router is that it can join a home or a business network (LAN) to the internet (WAN). The router will have an internet cable plugged into it, as well as having cables that the computers are connected on the LAN. The LAN connection could be wireless, creating a wireless router.

Proxy Server- It is a computer setup which is used to share a resource, usually an internet connection. Many other computers could request a web page via the proxy server. This proxy server will then be able to get the page using this internet connection, and it will pass it back to the computer that had requested it. Proxy servers are more commonly used instead of this router since additional software could get easily installed such  as an anti-virus or web filtering.

Bridge- This is a network device that can link two different parts of a LAN together. A router is usually linked to a LAN to a WAN (The Internet), and a bridge can independently link various parts of a LAN so they manage to act as a single LAN.

Firewall- A firewall is a device, or a piece of software that can be placed between your computer and the rest of the network (where the hackers are located). If you want to protect your LAN, you could place a firewall between the LAN and that internet connection. The job of the firewall is to block unauthorized connections that have been made to your computer or LAN. Normal would pass through the firewall, such as emails and web pages, but other data will get blocked.

Modem- A modem contains a DAC and an ADC. The DAC is required in the modem so the digital computer will be able to send data down an analogue telephone line (it converts digital data into noises which is exactly what the telephone line is designed to carry.) The ADC in the modem is required so that the analogue signals (noise) is exactly what the telephone has been designed to carry.


  • What is a server?
    • Computer holding data


  • The internet is a global network of computers

Internet Equipment

  1. A Computer
  2. Router
  3. Cables

What happens when you try to access a particular website?

  • You access a website and then your computer will ask permission and the server either denies you access or gives you access, and if it says yes you can see that website.
Term Definition
Network  Computers that are connected together in a site.
LAN   Local Area Network.
WAN  Wide Area Network.
Data Transmission  The process of sending digital or analog data over a communication medium to one or more computing, network, communication or electronic devices.
ISP  Internet Service Provider, you need this to access the interwebs.
MAC Address  Different on every computer and cannot be changed.
IP Address  Every single device has their own different IP Address.
URL  Contains IP Address and other details, stands for Uniform Resource Locator.
HTTP  Transfers web pages to client.
HTTPS  Secure web address (encrypted.)

Web Design Principles

  1. Simplicity

Keeping the website simple makes a good user experience. Don’t use too many colors. Don’t use too many font sizes. Add graphics to make your point, but don’t add too many.

  1. Visual Imagery

The look and feel of the website should be good, the content should be arranged and organized neatly. Use color to highlight certain elements if needed or to draw attention.

  1. Navigability

The web design should make it easy for users to find something. By clicking few clicks they should reach at the right content. If there are too many pages then a search box at the top right is very useful.

  1. Consistency

All pages of the web design should have same theme or layout and should be consistent. Important to keep background, color, font consistent.

  1. Accessibility

Ensure the website is accessible on various devices such as iPad, iPhone etc. These days lot of people use smartphones so the content should display well on smartphones or tablets.

  1. Conventionality

Follow some well known conventions to avoid confusion. For example, main navigation should be at the top. The Logo should be at the top. Clicking on the Logo should take to the home page.

  1. Credibility

Be honest about the content. Be clear and straight to point on what you are trying to explain. If you are selling something, then it is good to have prices listed. This helps people make choices and decisions. If you do not display price, it is likely that people will not come back.

  1. User-Centricity

Design the web with the people in mind, what they will like. It is important to remember that you have designed the web for someone else and not for yourself.

CMS (Content Management System)

A content management system (CMS) is a computer application that supports the creation and modification of digital content. It is often used to support multiple users working in a collaborative environment.

A web content management system (WCM or WCMS) is a CMS designed to support the management of the content of Web pages. Most popular CMSs are also WCMSs. Web content includes text and embedded graphics, photos, video, audio, maps, and program code (e.g., for applications) that displays content or interacts with the user.

CMS Advantages

  • Reduced need to code from scratch
  • The ability to create a unified look and feel
  • Version control
  • Edit permission management

CMS Disadvantages

  • Limited or no ability to create functionality not envisioned in the CMS (e.g., layouts, web apps, etc.)
  • Increased need for special expertise and training for content authors



HTML stands for Hyper-Text Markup Language. This can be used for creating web pages and web applications. Hyper-Text Markup Language (HTML) is a standardized system that is used for tagging text files to get font, color, graphic, and hyperlink effects on World Wide Web Pages. You can use CSS and JavaScript.

CSS stands for Cascading Style Sheets. CSS describes how HTML elements are to be displayed on screen, paper, or in other media. CSS saves a lot of work. It can control the layout of multiple web pages all at once.

Many web servers receive HTML Documents that have been saved from a webserver or from local computer storage.

<!DOCTYPE html>

< html>

< body>

<h1>My First Heading</h1>

<p>My first paragraph.</p>


< /html>

HTML Tag Definition: A html code that is defining every structure on a HTML page. This is including the placement of text and the images and hypertext links. Many HTML tags begin with the less-than character symbol. This ends with the greater-than symbol. The symbols are called angle symbols.

Definition and Usage. The <html> tag tells the browser that this is an HTML document. The <html> tag represents the root of an HTML document. The <html> tag is the container for all other HTML elements (except for the <!DOCTYPE> tag).


HTML Element Definition:  An HTML element is defined by a starting tag. If the element contains other content, it ends with a closing tag. For example <p> is starting tag of a paragraph and </p> is closing tag of the same paragraph but <p>This is paragraph</p> is a paragraph element.

HTML Element

HTML Attributes Meaning: A HTML attribute is a modifier of a HTML element type. A HTML attribute is added to a HTML start tag.

  • All HTML elements can have attributes
  • Attributes provide additional information about an element
  • Attributes are always specified in the start tag
  • Attributes usually come in name/value pairs like: name=”value”

The lang Attribute

The language of the document can be declared in thetag.

The language is declared with the lang attribute.

Declaring a language is important for accessibility applications (screen readers) and search engines: