Networks and the effects of using them - Mr Mark's ICT Website

Networks and the effects of using them

What is a network?

A network is two or more computers, or other electronic devices, connected together so that they can exchange data.

For example a network allows computers to

Share files.

Message each other.

Share a single printer.

Share online resources

Store data centrally

Make us of online services.

Online banking

Shopping online

Entertainment

Social media

Network connections between computers are typically created using cables (wires).

However, connections can be created using

Radio signals (wireless / wi-fi),

Telephone lines (and modems)

Satellite links.

Different types of network computers.

There are 2 types of network computers:

Servers

Clients

Servers

Servers are special, powerful computers that provide ‘services’ to the client computers on the network.

These services might include:
Providing a central, common file storage area Sharing hardware such as printers Controlling who can or can’t have access the network Sharing Internet connections Servers are built to be very reliable. This means that they are much more expensive that normal computers.

In a small network one server might provide all of these services.

In a larger network there might be many servers sharing the work.

Clients

Different types of Network

LAN (Local Area Network)

A Local Area Network is a network confined to one building or site.

Often a LAN is a private network belonging to an organisation or business.

Because LANs are geographically small, they usually use cables or low-power radio (wireless) for the connections.

WLAN (Wireless Local Area Network)

A wireless LAN (WLAN) is a LAN that uses radio signals (WiFi) to connect computers instead of cables.

At the centre of the WLAN is a wireless switch or router - a small box with one or two antennas sticking out the back - used for sending and receiving data to the computers. (Most laptops have a wireless antenna built into the case.)

It is much more convenient to use wireless connections instead of running long wires all over a building.

However, WLANs are more difficult to make secure since other people can also try to connect to the wireless network. So, it is very important to have a good, hard-to-guess password for the WLAN connections

WAN (Wide Area Network

A Wide Area Network is a network that extends over a large area.

A WAN is often created by joining several LANs together, such as when a business that has offices in different countries links the office LANs together.

Because WANs are often geographically spread over large areas and links between computers are over long distances, they often use quite exotic connections technologies: optical fibre (glass) cables, satellite radio links, microwave radio links, etc.

Bluetooth (WPAN) Wireless Personal Network

Bluetooth is a wireless networking technology designed for very short-range connections (typically just a few metres).

The idea of Bluetooth is to get rid of the need for all of those cables (e.g. USB cables) that connect our computer to peripheral devices such as printers, mice, keyboards, etc.

Bluetooth devices contain small, low-power radio transmitters and receivers. When devices are in range of other Bluetooth devices, they detect each other and can be 'paired' (connected)

Typical uses of Bluetooth:

Connecting a wireless keyboard to a computer

Connecting a wireless mouse to a computer

Using a wireless headset with a mobile phone

Printing wirelessly from a computer.

Transferring data / music from a computer to an MP3 player

Transferring photos from a phone / camera to another device

Because Bluetooth networking only works over very short distances, and with devices belonging to one user, this type of network is sometimes called a 'Personal Area Network'

Network Hardware

What is a router?

A router is used to enable data to be sent (routed) between different types of network. For example a between a

LAN (Local Area Network)

and a

WAN. (Wide Area Network)
Is is the most common use as they are used to connect to the internet.

They connect through cables or wireless.

What does a router do?

Routers are intelligent and perform the following functions:

Read data and decide where to send it

They decide the fastest route.

They can make the data be the suitable format for the network they are sending the data to.

What is an IP address?

An IP address, or simply an "IP," is a unique address that identifies a device on the Internet or a local network.

It allows a system to be recognized by other systems connected via the Internet protocol.

Each to the devices on the network have a different IP address which are normally only different by their last few digits.

All devices on the same network will share the same first few digits.

Laptop - 65.124.87.100

Smartphone - 65.124.87.101

Tablet - 65.124.87.102

How does the router store these IP address?

Routers store IP addresses in a routing table

The routing table lists all the different routes to other networks

The router uses this table to work out which is the best route when sending data to another network.

Routers send packets of data between computers on different networks

Each packet contains the specific IP address

A packet of data can pass through many networks to get to its final destination

Network Interface Card (NIC)

Any computer that is to be connected to a network, needs to have a network interface card (NIC).

Most modern computers have these devices built into the motherboard, but in some computers you have to add an extra expansion card (small circuitboard)

Some computers, such as laptops, have two NICs: one for wired connections, and one for wireless connections (which uses radio signals instead of wires)

Network Cables

To connect together different devices to make up a network, you need cables.

Cables are still used in most networks, rather than using only wireless, because they can carry much more data per second, and are more secure (less open to hacking).

Hubs

A hub is a device that connects a number of computers together to make a LAN.

The typical use of a hub is at the centre of a star network (or as part of a hybrid network) - the hub has cables plugged into it from each computer.

A hub is a ‘dumb’ device: if it receives a message, it sends it to every computer on the network. This means that hub-based networks are not very secure - everyone can listen in to communications.

Hubs are old technology and most days people use "Switches"

Switches

A switch, like a hub, is a device that connects a number of computers together to make a LAN.

The typical use of a switch is at the centre of a star network (or as part of a hybrid network) - the switch has cables plugged into it from each computer.

A switch is a more ‘intelligent’ device than a hub: if it receives a message, it checks who it is addressed to, and only sends it to that specific computer. Because of this, networks that use switches are more secure than those that use hubs, but also a little more expensive.

How do switches work?

Each network device has a MAC address (Media Access Control). This is used to identify the device on the network.

Data sent to the switch contains both the sending MAC address and the receiving address.

The switch will check the address and only send to the correct device.

Because the switch only sends to the correct address it reduces the amount of network traffic and increases the network speed.

Bridge

A bridge is a network device that typically links together two different parts of a LAN.

Whereas a router is usually used to link a LAN to a WAN (such as the Internet), a bridge links independent parts of a LAN so that they act as a single LAN.

Modem

Before the days of broadband Internet connections, most computers connected to the Internet via telephone lines (dial-up connections).

The problem with using telephone lines is that they are designed to carry voices, which are analogue signals. They are not designed for digital data.

The solution was to use a special device to join the digital computer to the analogue telephone line. This device is known as a modem.

A modem contains a DAC and an ADC.

Analogue to Digital Convertor (ADC)
If you want to attach an analogue input device to a digital device such as a computer, you will need an analogue to digital convertor (ADC).

A good example of a computer peripheral that requires an ADC is a microphone. When you plug a microphone into a computer, you are actually plugging it into an ADC which converts the analogue signals from the microphone into digital data that the computer can then process.

Digital to Analogue Convertor (DAC)
If you want to attach an analogue output device to a digital device such as a computer, you will need a digital to analogue convertor (DAC).

A good example of a computer peripheral that requires a DAC is a loudspeaker or headphones. When you plug a loudspeaker into a computer, you are actually plugging it into a DAC, which takes digital data from the computer and converts it into analogue signals which the loudspeaker then converts into sound.

The DAC in the modem is required so that the digital computer can send data down the 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 (noises) that arrive via the telephone line can be converted back into digital data.

So, simply put, a modem is required because computers are digital devices and the telephone system is analogue. The modem converts from digital to analogue and from analogue to digital.

What is the Internet?

The Internet, sometimes called simply "the Net," is a worldwide system of computer networks -- a network of networks in which users at any one computer can, if they have permission, get information from any other computer

Physically, the Internet uses a portion of the total resources of the currently existing public telecommunication networks. Technically, what distinguishes the Internet is its use of a set of protocols called Transmission Control Protocol/Internet Protocol (TCP/IP).

The Internet can be seen as having two major components: network protocols and hardware. The protocols, such as the TCP/IP suite, present sets of rules that devices must follow in order to complete tasks.

Without this common collection of rules, machines would not be able to communicate. The protocols are also responsible for translating the alphabetic text of a message into electronic signals that can be transmitted over the Internet, and then back again into legible, alphabetic text.

Hardware, the second major component of the Internet, includes everything from the computer or smartphone that is used to access the Internet to the cables that carry information from one device to another. Additional types of hardware include satellites, radios, cell phone towers, routers and servers.

The Internet provides the network connections that links computers together.

There are many ways that we can use these connections:

View web pages on the WWW (World-Wide Web)
Sending and receiving e-mail messages
Sharing files Communicating using voice (VOIP) and video (video-conferencing)
Playing multi-player games
Listening to streamed music or watching streamed video

What is an Intranet?

An intranet is the name given to a private network that provides similar services to The Internet: e-mail, messaging, web pages, etc.

However, these services are only for the users of the intranet – they are private, not public (unlike Internet services which are generally public).

Businesses and other organisations often have intranets for use by their employees.

Typical uses of an intranet would be:

Viewing internal web pages (e.g. company calendars, etc.)
Internal e-mail and instant-messaging between workers
Sharing of internal documents

Compare Internet & Intranet

What is a firewall?

Connecting to the internet

There are 4 main devices commonly used to connect to the internet. See below the advantages and disadvantages of each.

Download and complete this activity sheet and then upload to your Weebly

Wifi

Wi-Fi is the name of a popular wireless networking technology that uses radio waves to provide wireless high-speed Internet and network connections.

Wi-Fi networks have no physical wired connection between sender and receiver by using radio frequency (RF) technology -- a frequency within the electromagnetic spectrum associated with radio wave propagation. When an RF current is supplied to an antenna, an electromagnetic field is created that then is able to propagate through space

The cornerstone of any wireless network is an access point (AP). The primary job of an access point is to broadcast a wireless signal that computers can detect and "tune" into. In order to connect to an access point and join a wireless network, computers and devices must be equipped with wireless network adapters.

Bluetooth

Bluetooth is a short-range wireless communication technology that allows devices such as mobile phones, computers, and peripherals to transmit data or voice wirelessly over a short distance. The purpose of Bluetooth is to replace the cables that normally connect devices, while still keeping the communications between them secure.

Bluetooth uses less power and costs less to implement than Wi-Fi. Its lower power also makes it far less prone to suffering from or causing interference with other wireless devices in the same 2.4GHz radio band.

Compare Wifi and Bluetooth

How to setup and configure a small network

If you were asked to build a small, Internet-connected network from scratch, what would you need to do?

You would need to buy some hardware:

One or more switches / hubs - to link devices together

Network cables to connect devices to the switch, etc.

A separate wireless access point (or this could be part of the switch) - to allow wireless devices (e.g. laptops or smart-phones) to join the network

A router to connect your LAN to the Internet (WAN)

A firewall to protect your network from hackers

Possibly a bridge if you already have a section of network and you want your new network to connect to it
Server(s) to manage network functions such as network security, network file storage, shared resources (such as printers)

You would need to organise some other things:

Set up an account with an Internet Service Provider (ISP)

Get an Internet connection installed from the ISP to your location

Configure various bits of hardware and software so that everything worked with the network

Network Security

Network security is the process of taking physical and software preventative measures to protect the underlying networking infrastructure from unauthorized access, misuse, malfunction, modification, destruction, or improper disclosure, thereby creating a secure platform for computers, users, and programs to perform their permitted critical functions within a secure environment.

As soon as your computer is connected to a network, you have to start thinking about security – security of your files, information, etc.

A network allows a person who does to have physical access to your computer (they are not sitting in front of it) to gain access all the same. If your computer is connected to a network, other people can connect to your computer.

A person who gains unauthorised access to a computer system is often called a hacker.

Security Issues

Hacking

Hacking is identifying weakness in computer systems or networks to exploit its weaknesses to gain access.

They do this for many reasons including:

To cause damage to data by deleting/changing it.
To commit fraud by stealing data
To access private information
For fun.

Hacking techniques used.

The easiest way for a hacker to gain access to your network/private data is to get your password or user details and simply login as though they were authorized. They can get your details by using tricks that make you give them your details. Examples of these are:

Phishing

Phishing is a cyber attack that uses disguised email as a weapon.

The goal is to trick the email recipient into believing that the message is
—something they want or need
— a request from their bank, for instance, or a note from someone in their company
— and to click a link or download an attachment.

What really distinguishes phishing is the form the message takes: the attackers masquerade as a trusted entity of some kind, often a real or plausibly real person, or a company the victim might do business with.

It's one of the oldest types of cyberattacks, dating back to the 1990s, and it's still one of the most widespread and pernicious, with phishing messages and techniques becoming increasingly sophisticated.

How to stay safe from Phishing

Pharming

Pharming is yet another way hackers attempt to manipulate users on the Internet.

While phishing attempts to capture personal information by getting users to visit a fake website, pharming redirects users to false websites without them even knowing it.

While a typical website uses a domain name for its address, its actual location is determined by an IP address. When a user types a domain name into his or her Web browser's address field and hits enter, the domain name is translated into an IP address via a DNS server.

The Web browser then connects to the server at this IP address and loads the Web page data.

After a user visits a certain website, the DNS entry for that site is often stored on the user's computer in a DNS cache. This way, the computer does not have to keep accessing a DNS server whenever the user visits the website.

One way that pharming takes place is via an e-mail virus that "poisons" a user's local DNS cache. It does this by modifying the DNS entries, or host files. For example, instead of having the IP address 17.254.3.183 direct to www.apple.com, it may direct to another website determined by the hacker.

Pharmers can also poison entire DNS servers, which means any user that uses the affected DNS server will be redirected to the wrong website.

Fortunately, most DNS servers have security features to protect them against such attacks.

Protect yourself from Pharming

Securing data online

Digital Certificates

A digital certificate, also known as a public key certificate, is used to cryptographically link ownership of a public key with the entity that owns it.

In other words it is a certificate that proves the authenticity of the sender.

Digital certificates are for sharing public keys to be used for encryption and authentication.

They include:

Name of the sender
Senders E-mail address
A serial number (encrypted)
An expiry date

An SSL certificate, or secure certificate, is a file installed on a secure Web server that identifies a website.

This digital certificate establishes the identity and authenticity of the company or merchant so that online shoppers can trust that the website is secure and reliable.

In order to verify that these sites are legitimate (they are who they say they are), the companies and their websites are verified by a third party, such as Verisign or Thawte.

A padlock icon, or lock icon, displayed in a web browser indicates a secure mode where communications between browser and web server are encrypted.

This type of connection is designed to prevent anyone from reading or modifying the data you exchange with the website.