Identify network hardware and protocols
Identify network hardware and protocols Identify network hardware and protocols
Identify network hardware and protocols
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Contents
1 Layered network protocols 2 TCP/IP reference model 3 Application layer 4 Transport layer 5 Internet layer 6 Network access layer 7 Network hardware
7.1 Transmission media 7.2 Network devices
8 Network address translation 9 Using networks securely 10 Malware 11 Phishing 12 Activities 13 Resources 14 End of course quiz 15 Acknowledgements
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Identify network hardware and protocols
1 Layered network protocols Network communication relies upon the interaction of
many different protocols. These protocols are
designed to implement a particular set of rules and
conventions governing particular aspects of how
devices in a network communicate.
Network protocols are arranged in layers, with each
layer providing a specialised service for the layer
above. Because each layer consists of standardised
protocols that perform functions to an agreed set of
rules, it is possible to modify individual protocols
within a layer without having to change protocols in
other layers.
To visualise this concept of layers, consider a
conversation between two people:
Content layer: ideas exchanged in
conversation.
Rules: agree to speak a common
language, take turns speaking, not to
interrupt when others are speaking.
Physical: face-to-face communication
requires speakers to be close enough to
hear each other.
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In this example, the conversation has been divided
into three layers. The physical layer considers the
fundamental requirements of exchanging information
between two people using speech. This includes
considering the distance between the speakers, which
will affect how loud each person needs to talk in order
for the other to hear. Speech is a movement of air,
which is translated as sound waves. This means that
the conversation could take place in a ‘near’ vacuum
like outer space.
The rules layer defines how the speakers will talk. To
exchange information, a common language would
need to be chosen. Once the language is agreed, how
is the conversation to be managed? Taking turns is a
reasonable way to converse with another person and
interrupting would be considered rude. But what
happens if one person misses something and wishes
it to be repeated? Do they ask for it to be repeated
verbally, or do they use an agreed signal such as
raising a hand?
The content layer considers the actual message
exchanged between the two speakers, which in a
conversation may be an item of news, plans for a
holiday or just gossip.
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By dividing the conversation into layers, we have
decided upon the particular functions that are required
by each layer to support communication, and in our
simple layered model, it should be possible to change
some aspects within one layer without affecting the
others. For example, if we now decide to have a
telephone conversation, how does this change the
requirements of our physical layer?
Networking protocols can be layered in a similar
manner to the voice conversation in the example
above, but has a wider range of considerations and
uses different terms:
Encoding: language to use.
Formatting: greeting, recipient identity,
closing phrase, sender identity.
Message size: segmentation of data.
Timing: flow control and timeout.
Delivery: to one host (unicast), to all
hosts (broadcast), to some hosts
(multicast).
We will discuss these terms in more detail as you
progress through the course.
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2 TCP/IP reference model The protocols used within the Internet were designed
using a layered model referred to as the TCP/IP
reference model:
Figure 1
These protocols operate on your computing devices,
and allow the programs you use to access the data
network via the single network interface card (NIC)
that is fitted to most devices. Imagine how difficult this
task would be for your device if you used multiple
programs that required network access – for example,
surfing the World Wide Web (WWW), downloading a
file and sending an email.
All these different programs expect to be able to
simultaneously access your NIC in order to send and
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receive data. The purpose of the TCP/IP reference
model is to allow the design and creation of protocols
that can support the network requirements of various
installed programs competing for the attention of a
single NIC.
Each layer of the model defines the function of the
protocols that operate within it:
Application: provides the interface
between the other layers and the
operating system software on your
computing device.
Transport: manages application layer
data and prepares it for transmission by
segmenting it into easily manageable
blocks. It is also responsible for allowing
multiple programs to simultaneously
access the NIC, and managing the
reliable delivery of data if required.
Internet: manages the delivery of data
encapsulated in packets across
networks.
Network access: manages the delivery
of data across local network media,
regardless of the physical media type.
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Groups of protocols that are created in accordance
with a protocol model are referred to as a protocol
suite. The TCP/IP protocol suite operates in
accordance with the TCP/IP reference model, and it is
the predominant suite used within the Internet.
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3 Application layer The application layer consists of many different
protocols because it needs to provide an interface
between the many different application programs that
may be installed on a device.
The protocols in the application layer ensure that data
is exchanged between devices using an agreed
format and in an agreed manner.
Some common application protocols and the programs
they support include:
Simple Mail Transfer Protocol (SMTP): used by email programs such as Outlook
and Thunderbird when they need to send
emails.
Post Office Protocol 3 (POP3): used by
email programs when they need to
receive emails.
Hyper Text Transfer Protocol (HTTP): used by web browsers such as Edge and
Firefox to request and transfer webpages
from the WWW.
File Transfer Protocol (FTP): often used
by file sharing programs in order to send
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and receive files between users across
the Internet.
Figure 2
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4 Transport layer The data from multiple application layer protocols
cannot just be passed on to the lower layers in a
single block, as this would lead to severe delays in
sending data to the NIC.
To visualise this problem, imagine you are heading to
the till in a supermarket. Some shoppers have heavily
loaded trolleys, and it takes several minutes to scan,
bag and pay for all their items. Customers with fewer
items use the ‘ten items or less’ queue, and although
there may be more people in line, they are each
served much more quickly than those in the queue for
trolleys. Now imagine there is only one queue, and the
customers with a few items are forced to queue
alongside those with a trolley. The customers with
only a few items have to wait longer to be served.
This is exactly the same problem faced by the
application layer protocols, as they all send different
sized blocks of data to the NIC. FTP may try to send a
file measured in megabytes, whereas SMTP may
send an email of only a few kilobytes. If FTP gets its
data to the NIC first, then transmission of the email is
substantially delayed.
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One of the primary jobs of the transport layer is to
divide all the data received from the application layer
protocols into equal segments, which can then be
mixed together (multiplexed) and passed to the next
layer for processing. This process ensures that all
protocols receive an equal share of the capacity of the
device’s NIC.
Figure 3
Once the data is divided into segments it needs to be
tracked so that if they are delivered out of sequence,
or some get lost, then steps can be taken to re-order
or recover them. The transport layer thus
encapsulates the segments it creates with a header,
which contains sequence numbering to allow for
segment tracking.
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When segments are received, they need to be placed
in the correct order to recover the original data that
was sent, but this takes time, and if your device is
receiving segments from multiple applications it can
get extremely busy and may not be able to cope,
leading to data loss. To prevent this, the transport
layer can implement flow control, which allows a
device receiving segments to limit the number of
segments that are sent to it from a transmitting device.
The two most common transport layer protocols of
TCP/IP are Transmission Control Protocol (TCP) and
User Datagram Protocol (UDP).
Both protocols manage the communication of
multiple applications.
The differences between the two centre on the specific
functions each protocol implements.
TCP provides reliable delivery of data,
therefore it supports all the functions
described above – segmentation,
multiplexing, sequencing and flow control.
The disadvantages of using TCP is that,
due to its complexity, it can introduce
unwanted delays between
communicating devices.
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UDP provides rapid delivery of data, but
without reliability. UDP only provides
segmenting and multiplexing of data
received from the application layer. Data
from communication programs using
voice and video are typically intolerant of
delay and therefore use UDP.
Figure 4
Both TCP and UDP keep track of the application layer
protocols they handle by using port numbers, which
act like doorways between the transport and
application layers. These range from 1 to 65535, and
protocols are associated with individual port numbers:
SMTP: port 25
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POP3: port 110
HTTP: port 80
FTP: ports 20 and 21
How ports operate is slightly more complex than
indicated above, as only server processes use fixed,
or well-known ports. Client processes (e.g. a web
browser) using HTTP will select a random, unused
port. This process will be examined in more detail in a
later module.
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5 Internet layer This layer allows computing devices to exchange data
across networks. It receives segments of data from
the transport layer protocols and encapsulates them
within packets. The packets contain address
information identifying the source and destination
devices, allowing packet switching devices such as
routers to route them to the correct destination
network.
There are two Internet layer protocols currently in use:
Internet Protocol v4 (IPv4): this is the most
popular TCP/IP Internet layer protocol,
which uses 32-bit addresses,
superseding historically previous
versions. The networking industry is
slowly phasing out IPv4 due to the rapid
growth of the Internet and the increasing
demand for IP addresses, which it can no
longer support. However, this will take
considerable time as there are many
systems and devices still dedicated to
IPv4.
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Internet Protocol v6 (IPv6): this is the
replacement for IPv4. It uses a 128-bit
address and is capable of supporting the
expected future growth of devices
connecting to the Internet.
The switchover from IPv4 to IPv6 was facilitated by the
layered approach to network protocols. Because IPv6
can perform the same function as IPv4, there was no
requirement to redesign the protocols above (TCP
and UDP) or below the Internet layer.
Figure 5
Activity: Compare IPv4 to IPv6As you have seen previously, bits are meaningful: the number of
bits used increases the size of a network or the number of
addresses available.
1. Go to Google and enter this search term: 2^32. (The
up arrow or power symbol can be found by pressing
shift+6.) Write down the result:
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Provide your answer... 1. Now search for 2^128 on Google and record the
result: Provide your answer...
1. Which number is the biggest and why?Provide your answer...
1. What does the 'e+38' mean in 2^128?Provide your answer...
1. What is the name of this number? (Hint: you will have
to research the answer.)Provide your answer...
1. Now try 2^128 in Wolfram Alpha.
Provide your answer...
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6 Network access layer This layer is responsible for preparing the data
packets it receives from the Internet layer for
transmission to the physical media connecting devices
within the local network. There are three main types of
physical media available:
Copper: coaxial, twisted pair.
Optical: single mode, multi-mode.
Wireless: WiFi, satellite.
Due the wide range of media, and supported
technology, the network access layer is more complex
than the other layers. Additionally, while the upper
layer protocols within the TCP/IP suite are
implemented in software, the network access layer
must provide physical connectivity, thus it has both
hardware and software components, typically
implemented within a device’s NIC.
The primary functions of the network access layer are:
Accepting packets from IP and
encapsulating them within frames.
Different protocols can use different types
of frames.
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Converting the binary bits that make up
the frame into a signal suitable for the
type of media that is in use. For example,
the bits are converted into an electrical
signal for copper media and into pulses of
light for optical media. Bits are converted
to ultra high frequency radio waves on a
wireless network.
Whereas the upper layer protocols are controlled by
the agencies charged with maintaining the Internet
(primarily the Internet Engineering Task Force), the
sheer number of physical media available has led to
many different protocols being designed and
produced, often by commercial organisations.
Figure 6
Over time, many of these protocols have become
standardised and thus have become available for
general use. The most commonly used network
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access Local Area Network (LAN) protocol is
Ethernet and its derivatives.
The frames used by Ethernet totally encapsulate the
IP packets sent from the network layer, so devices
cannot directly read the IP addresses they contain.
This makes it necessary for frames to carry their own
source and destination addresses to ensure frames
are delivered to the correct devices in the local
network.
In an Ethernet network, this address is known as a
Media Access Control (MAC) address.
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7 Network hardware A network is made up of hardware, which can be
categorised as either:
transmission media
devices.
Hardware devices make forwarding decisions to send
data between user devices across interconnecting
pathways created using copper, optical or wireless
transmission media.
7.1 Transmission media Most home networks use a combination of copper
and wireless transmission media to interconnect
devices.
The copper wiring normally used to support the
operation of Ethernet within homes is referred to as
unshielded twisted pair (UTP). This consists of four
insulated twisted copper pairs within a protective outer
jacket:
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Figure 7
The advantages of using UTP in the home is that pre-
made cables are easily available, and they are
cheaper than coaxial cables, which they have largely
replaced.
One disadvantage of UTP is that it is vulnerable to
electromagnetic noise signals. Noise signals are
created by other electromagnetic sources, such as
power cables, lighting and power tools.
Electromagnetic noise can appear on the UTP copper
pair and interfere with the data signals it is carrying.
This can lead to data loss or data corruption.
To minimise the effects of noise, the copper pairs are
twisted together, which helps cancel out noise signals
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travelling down the pair. Additionally, UTP cable
lengths are limited to 100m when carrying Ethernet to
guarantee that they can support the required data
rates in the presence of noise.
UTP cables have to be wired correctly to allow the
twisted pairs to perform noise cancellation, and this is
achieved using a standard plug, called an RJ45, and a
particular wiring convention. A correctly built UTP
cable with an RJ45 connector can be connected to the
Ethernet NIC ports of most devices:
Figure 8
Wireless is a very popular transmission media within
home networks, as the lack of physical cabling makes
connecting new devices relatively straightforward. In a
home environment, the WiFi system requires a WiFi
NIC fitted to the user’s computing device, allowing it to
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connect to a compatible wireless access point (WAP),
which will itself generally connect to the rest of the
network using a UTP connection:
Figure 9
WiFi is a popular network access technology as it is
derived from Ethernet, and there are many devices
available that provide both Ethernet and WiFi
capability. This is especially true at home, as the
‘home router’ you use to connect to your Internet
Service Provider (ISP) will provide both Ethernet and
WiFi connectivity, as it contains an integrated WAP.
WiFi wireless is also affected by noise signals, but to a
far greater degree than UTP as it is impossible to
protect a wireless signal from external interference.
Whereas UTP will guarantee a fixed data rate over
100m, the rate achieved over wireless will steadily
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reduce as the user device moves away from the
access point.
WiFi introduces another serious problem, as the signal
it produces does not stop when it reaches the limits of
your property. This makes it possible for other people
to ‘hijack’ your network by connecting to it wirelessly.
It is therefore extremely important to use some form of
security, such as a password, to prevent such access.
7.2 Network devices Networks require a variety of different devices, each
with a particular function, in order to provide
connectivity and data forwarding. In a home network,
the router provided by your ISP will provide all these
functions, but in larger networks within businesses
and schools, discrete devices are required.
7.2.1 Switches Switches provide connectivity points within a network,
allowing you to add a large number of devices to a
network, typically using UTP cabling. Because the
most common network access protocol is Ethernet,
most switches will support it and are thus referred to
as Ethernet switches. Ethernet switches have now
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largely replaced the older and much slower Ethernet
hubs.
Figure 10
Switches provide multiple Ethernet NICs, which are
referred to as ports. You can use a UTP cable to
connect multiple computing devices to the ports:
Figure 11
The term used to describe the layout of your devices is
‘network topology’. The simple layout shown above is
referred to as a star topology, as it resembles a multi-
pointed star. Note that each of the UTP cables shown
must be no longer than 100m.
The number of computing devices you can connect
using a single switch is limited to the number of ports
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that are available. If you need to add more devices, or
you wish to extend the size of your network, you can
connect two switches together. This topology is
referred to as an extended star:
Figure 12
The Ethernet network access protocol was originally
designed to support data rates of 10Mbps. This is too
slow to support modern networks, so the protocol has
evolved to support greater data rates.
Most Ethernet switches are capable of supporting
several Ethernet variants on each port. Although it is
possible to configure each port to operate at a
particular data rate, most Ethernet switches will
negotiate with the connected computing device and
set themselves to the highest data rate that they both support. It is best practice to connect switches
together using the fastest data rate port available.
Switches forward data between computers using the
destination MAC addresses contained in the frames
they receive. This means that switches have no
knowledge of the IP addresses of the packets
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contained within the frames, so they cannot be used
to join together different IP networks. Referring to the
diagram below, all the PCs are addressed within the
same IP network and the switches will successfully
forward data between them.
Figure 13
The diagram below shows the same topology, but this
time the PCs have been placed in different IP
networks. While the switches will forward data
between the PCs based on the MAC addresses in the
Ethernet frames, the PCs will refuse to communicate
with devices outside their own IP network.
Figure 14
Activity: Data ratesResearch the data rates supported by the following Ethernet
variants:
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Protocol Data rateEthernet 10MbpsFast Ethernet Provide your answer... Gigabit Ethernet Provide your answer... 10 Gigabit Ethernet Provide your answer...
7.2.2 Routers Routers provide connectivity between different IP
networks and are responsible for forwarding IP
packets based on their destination IP addresses. It is
the job of the router to connect many different
networks – this is how the internet operates. Routers
provide multiple Ethernet NICs, which are referred to
as interfaces. Typical routers do not have many
interfaces, as they are not designed to provide
connectivity between different IP networks rather than
for individual hosts.
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Figure 15
Each router interface must be addressed with an IP
address within the network to which they connect.
This IP address will act as the default gateway
address configured on all the host devices within the
IP network:
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Figure 16
Although Ethernet is the most common network
access protocol you will meet in LANs, there are many
other types of protocols available, especially within
Wide Area Networks (WANs). Because routers are
designed to connect networks together, they must be
capable of supporting multiple network access
protocols. Some routers are specifically designed to
connect to particular types of WANs, whereas others
are modular in design, allowing you to add the correct
NIC for the WAN network access protocol in use.
7.2.3 Wireless Access Points (WAP) You can send data directly between two devices using
WiFi provided that the devices have compatible
wireless NICs fitted. This is very useful if you wish
create a temporary connection between the devices,
but it can prove difficult to manage as you try to
connect more devices.
Using a wireless access point in your network provides
a central WiFi connection point to which all WiFi
capable devices must connect in order to exchange
data. In effect, you have created a star topology
without wires:
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Figure 17
While a single star topology WiFi network can be
useful, you are more likely to meet WAPs connected
to Ethernet switches, allowing the network to provide
both wired and wireless network access:
Figure 18
7.2.4 Modem
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The function of a modem is to MOdulate and
DEModulate data to and from a transmission media.
In the early days of the Internet, computers sent
binary bits, which alternated between 0 and 5v,
towards an ISP using the telephone system, which
was (and still is) designed to process audio signals
from telephones.
The modem was required to convert the binary
electrical signal from the computer into an audio
signal suitable for transmission over the telephone
system, and vice versa. So it was used to modulate
data onto the phone line, and demodulate data
received from the phone line:
Figure 19
You will not see many individual modems in modern
networks as they are now integrated within other
devices, such as home routers. They are still needed
as home Internet access via Digital Subscriber Line
(DSL) utilises the telephone system, albeit using
different frequencies. Cable Internet providers also
utilise modems, as the binary electrical signal from a
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computer has to be converted into the radio
frequencies used within the cable transmission
system.
There are also some legacy systems that still require
modems, such as some older chip and pin systems.
Network engineers also use modems as a secret back
door into their networks, just in case the main
connection fails and they need to remotely find the
cause of the issue.
7.2.5 Home router If you have an Internet connection at home, you are
probably using a home router given to you by your
service provider. Although it is often referred to as a
router, it is actually a combination of all the devices
that we have discussed so far:
Wireless Access Point: provides
wireless connectivity for WiFi devices.
Switch: provides Ethernet ports for the
connection of devices using UTP cables.
Router: provides routing between the
home and ISP IP networks. Also
performs Network Address Translation
(NAT) and firewall security.
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Modem: converts the router output to a
format suitable for transmission over the
link used to connect to the ISP, usually
DSL or cable.
Figure 20
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8 Network address translation You will have read about NAT when exploring IP
packet forwarding, but it is covered in more detail
here.
If you examine the diagram below, you will see that the
home LAN is using IP addresses in IP network
192.168.0.0/24, which will be the case for all the ISP’s
customers who are using the same type of home
router. This will cause problems, as the source and
destination addresses have to be unique in every
communication unicast (sending packets between two
devices).
Figure 21
Why do home routers use the same address on the
home LAN if it will cause problems within the Internet?
Remember, IPv4 cannot provide sufficient IP
addresses for all the devices that want to use IP, so
certain ranges of IP address, including
192.168.0.0/16, are set aside as private addresses.
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Private IP addresses can be used by anyone, at any
time, within a private network. This addresses the
issue of not having sufficient IP addresses, but
creates a problem in that the IP address cannot be
used to communicate over the Internet as it is not
unique. However, you will have a unique, public IP
address assigned to your home router on the interface
that connects to the ISP, which in the diagram above
is 82.10.250.19.
The idea of NAT is to convert the source address
from all outgoing LAN packets into the unique public
address assigned to the home router, and vice versa
for incoming packets from the Internet.
IP addresses in packets The image below shows a packet transmitted from the
home PC towards the web server, which needs to be
routed towards the Internet by the home router:
Figure 22
Note that in the diagram above the source address is
192.168.0.101, which is private.
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The packet will be received by the home router, which
will perform NAT, converting the source address to its
own WAN interface IP address (82.10.250.19):
Figure 23
The packet can now be forwarded through the Internet
to the destination web server, which will return the
requested webpage in a series of packets:
Figure 24
The IP packet is now addressed with the web server
acting as the source, and the public address of the
home router WAN interface as the destination. The
home router will accept the incoming packet, and
translate the destination address back to the private
IP address of the home PC:
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Figure 25
The use of NAT and private IP addresses has
extended the life of IPv4 well beyond what would have
been possible with the original range of addresses it
provided. Private IP addresses and NAT are
implemented within most home and business
networks.
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9 Using networks securely You need to consider the security of your home
network in order to protect your personal security. If
your network is not secured, or you use it in an
insecure way, then you increase the risk of threats to
yourself and your data.
Consider some of the activities that you undertake via
the Internet:
emailing
sending photographs
chatting
posting to wiki
shopping
banking.
What would be the impact if someone was able to
intercept any information you sent while doing these
activities? It could range from personal
embarrassment to severe financial loss. You would
probably not do any of these things with a stranger sat
next to you, but when you do them over the Internet,
there is a risk that your data can be intercepted by
others.
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What could be the motivation for trying to access your
information? The list is long, but some popular
reasons are:
general nosiness
a wish to bully or get you into trouble
a wish to steal your money or data
a desire to impersonate you while carrying
out a criminal activity.
To start securing your network, consider the
passwords that you use to protect access to your
online accounts, and to your network devices such as
PCs, tablets and home routers.
Your passwords need to be strong. Use a
mix of numbers, letters and special
characters. Do not use anything that
could be guessed, such as a pet’s name
or a birthday.
You need to change your passwords
regularly in case other people learn them.
Do not tell your passwords to anyone.
Ever.
If you have set up a password hint, do not
make the hint too obvious.
Do not use the same password across
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someone learns it, they have access to
everything.
Do not write your passwords down.
You also need to consider how your devices handle
your passwords, as some will try to be helpful and
store them for you. If you are using a public computer
to access a website that requires you to enter a
password, the browser may offer to store it for you.
This is not a good idea, as the next user of the
computer can access your passwords.
If you log into your account and then walk off to do
something else, leaving the computer unattended,
anyone else who is present can access your account.
If you leave your PC or device, logout from it first.
Most PCs, tablets and smartphones can be configured
to automatically logout after a short period of
inactivity, so find out how to set this up.
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10 Malware Malware is a type of computer program created by
criminals with the intention of stealing or damaging
data and perhaps disrupting network operation. There
are three main types of malware:
1.Virus: malicious software attached to
another program to execute a particular
action on a computer. Viruses normally
require the intervention of humans in
order to propagate themselves, and are
commonly received as attachments to
emails or as files stored on USB memory
sticks.
2.Worms: self-contained malware programs
that attack a computer and try to exploit a
specific security ‘hole’ or vulnerability in a
software program installed on it. Once
they have successfully attacked the
vulnerability, the worm copies its program
across the network to attack other
devices on the network.
3.Trojan horse: similar in operation to a
worm, except it is disguised to look like a
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useful software program that you may
want to install on your computer. Once
you have installed the Trojan, it will act as
if it is normal software, but will be secretly
carrying out some criminal activity such
as logging the keys you are typing in an
attempt to copy your passwords. Trojans
are normally capable of transmitting the
information they steal to interested
criminals via your network connection to
the Internet.
There are many precautions you can take to protect
yourself from malware:
Always install antivirus software on your
computers and make sure it is kept up-to-
date.
Always keep your operating system
updated, as updates include patches for
any vulnerabilities that may be exploited
by malware. Most operating systems can
be configured to do this automatically for
you.
Never open email attachments from
people you do not know. Always scan
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email attachments from people you do
know.
Always scan your USB memory sticks with
your antivirus software after inserting
them into your computer. Never plug in a
memory stick that you have ‘found’.
Always keep copies (backups) of your
important files on a separate hard drive,
preferably one that is not kept connected
to your network. You can then retrieve
your data if malware damages the
originals.
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11 Phishing Many criminals will try to get you to reveal passwords
and other account information by pretending to be
someone else. This shouldn’t be an issue if you follow
the advice already covered in this course – in
particular that you should never share your
passwords. However, some criminals are very skilled,
and send emails and texts that appear to come from
legitimate sources, such as a bank or a government
agency:
Figure 26
These messages will normally direct you to a website,
which may appear very convincing but is designed to
capture all your login information. To protect yourself
from phishing, remember that legitimate organisations
do not conduct sensitive business via email or text –
they will generally use the telephone or send a letter.
When they do email, it will be a request for you to
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login to your account securely, so be suspicious of
any links to websites that could be run by fraudsters.
Always check the address bar of your web browser to
see which application layer protocol is being used to
send your sensitive information to a website.
Responsible organisations will use HTTPS, which is a
secure version of HTTP and can prevent your data
being intercepted by Internet-based criminals:
Figure 27
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12 ActivitiesActivity: Investigating your home networkMake sure you have your parent or carer’s permission to
investigate this at home. If you are doing this at school, make sure
you have permission from a teacher or IT Technician.
1. What devices are wired on your LAN via UTP cable?Provide your answer...
1. Does the cable go into an Ethernet switch or into
sockets and disappear?Provide your answer...
1. Where is the switch located?Provide your answer...
1. How do you know if it is an Ethernet switch?Provide your answer...
1. Do you have any wireless devices connected?Provide your answer...
1. Where is the wireless access point?Provide your answer...
1. How does your network connect to the Internet?Provide your answer...
1. What type of WAN connection does your network have
and what connectors does it use?Provide your answer...
1. Is there a modem and, if yes, where is it situated?Provide your answer...
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1. If at home can you find the address given to your
router from the ISP? (It is called your ‘public’ address.)Provide your answer...
1. How much you have learnt about networking?Provide your answer...
Activity: Network devices and protocols – Packet TracerWe connect our devices to the Internet and the Internet connects
them all together. But what is the Internet made of? We say it
interconnects all the devices, but how?
Network devices are mainly hubs, switches or routers. There are
lots of other specialist bits, but the bulk of the interconnectivity is
done by switches and routers. In this course you have looked at
client server models, web requests and emails. What do these
messages look like and how are they sent?
For each type of communication over the network there are a set
of rules and specifications as to what format and order the
information is sent. These are called protocols and they are
fundamental in understanding how the Internet works.
This Packet Tracer lab explores the devices and protocols used in
computer networks. You will need:
Lab Book: Identify Devices and Protocols Used in Computer Networks
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Packet Tracer CASBIT.pkz
Activity: Password hints Companies do not store a user’s passwords in clear text – they
send it through a scrambling algorithm to produce a 'hash', and the
hash is then saved. The hash algorithm does not work in reverse,
so you can't unscramble a hash to get the original password.
When you enter your password the site uses the same algorithm to
make a hash, which it then compares to the hash saved against
your details.
Some sites allow you to store password hints, and they save these
as clear text. Adobe was hacked in 2013, and its hashed
passwords and hints were stolen for thousands of customers. The
hackers looked at all the hints that gave the same hash (hence
were the same password). Because they had lots of hints for the
same password it was easy to guess what they were.
Can you guess the passwords used in this puzzle based on the
stolen hints?
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13 ResourcesFor more information, take a look at the following resources.
Watch this computer networking tutorial to explore
what is a protocol:
Watch the video at YouTube.com.
For a detailed look at the complexity of what happens
when you click a URL read Igor Ostrovsky’s blog post.
Read Google's guide to online safety.
Read How-To Geek’s guide to choosing a good password and watch the following video:
Watch the video at YouTube.com.
Read Action Fraud’s guide to phishing and watch
the following video:
Watch the video at YouTube.com.
Watch this video on being cautious when using public
WiFi:
Watch the video at YouTube.com.
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14 End of course quizNow it’s time to test what you’ve learned in a quiz.
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15 AcknowledgementsGrateful acknowledgement is made to the following sources:
Figure 1: Birmingham City University (BCU)
Figure 2: Birmingham City University (BCU)
Figure 3: Cisco
Figure 4: Birmingham City University (BCU)
Figure 5: Birmingham City University (BCU)
Figure 6: CommScope. This file is licensed under the Creative
Commons Attribution-Noncommercial-NoDerivatives Licence
http://creativecommons.org/licenses/by-nc-nd/2.0/
Figure 7: tlsmith1000. This file is licensed under the Creative
Commons Attribution-Share Alike Licence
http://creativecommons.org/licenses/by-sa/2.0/
Figure 8: Bull3t Hughes. This file is licensed under the Creative
Commons Attribution-Share Alike Licence
http://creativecommons.org/licenses/by-sa/2.0/
Figure 9: Cisco
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Figure 10: Cisco/Birmingham City University (BCU)
Figure 11: Cisco/Birmingham City University (BCU)
Figure 12: Cisco/Birmingham City University (BCU)
Figure 13: Cisco/Birmingham City University (BCU)
Figure 14: Cisco/Birmingham City University (BCU)
Figure 15: Cisco
Figure 16: Cisco/Birmingham City University (BCU)
Figure 17: Cisco/Birmingham City University (BCU)
Figure 18: Cisco/Birmingham City University (BCU)
Figure 19: Publisher unknown
Figure 20: Cisco/BCU
Figure 21: Birmingham City University (BCU)
Figure 22: Birmingham City University (BCU)
Figure 23: Birmingham City University (BCU)
Figure 24: Birmingham City University (BCU)
Figure 25: Birmingham City University (BCU) Page 57 of 58 29th August 2017
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Figure 26: Publisher unknown
Figure 27: Screenshot taken from Barclays, example of
phishing.
Every effort has been made to contact copyright holders. If any
have been inadvertently overlooked the publishers will be pleased
to make the necessary arrangements at the first opportunity.
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