Lecture notes complement
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Chapters 6, 7 and 8
lecture notes complement
for test 3
Dr. Nazih Abdallah - Modern business computer
Internet
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 Internetworking:
The basic idea behind Internet invention is connecting networks with each other
creating a network of networks (MAN or WAN).
 This process is known as internetworking and several technological steps were
already set up that guided to the Internet.
 Networks may have different topologies and different protocols and to connect
them we need to set up a conversion or translation service between them.
 Connecting networks:
 Two similar networks (same protocol) are connected by means of a bridge whose
job is to connect 2 or more segments and control packet flow between them.
 Two dissimilar networks (have different protocols) are connected by means of
gateway device which provide assistance to make sure the message flows
uniformly in both networks
 Network switch links segments of the network to bridges or gateways. Basic
switches don’t process data.
 A switch that does process data is called multilevel switch because it will be
working at a level 3 processing.
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Packet switching
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Internetworking technology will be impossible with circuit switching
that allows fewer messages to use the network pathways simultaneously.
Packet switching, on the other hand, optimizes the use of network
pathways by dividing each message into parcels of data called packets
whose trips take short time.
 Packets are sent from A to B using most available pathways
between them instead of only one like in circuit switching.
Consider the following scenario of 9 packets going from A to B.
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Packet1 takes itinerary I1
Packet2 takes Itinerary I2 and so on…
Packet9 takes Itinerary I9
Upon arrival to B, a guide will gather them regroup them and deliver them
altogether one message as they initially were.
 An internetwork is basically a small Internet the biggest
internetwork of all networks and internetworks is the Internet
that controls our daily life (as individual, community, society,
business, government and so on…)
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Internet protocol
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Internet protocol TCP/IP (Transmission Control
Protocol/Internet Protocol) was the right solution where
each part fulfills a specific job making the process very
fast to handle the huge number of exchanged packets:
TCP (Transmission Control Protocol) is the part that takes care of
the packet at the origin and destination making sure they are well
prepared at the origin and assemble them prior to the correct
delivery at the destination.
 TCP cuts the message into packets below 1500 bytes each because
Ethernet protocol in LANs cannot take more than 1500 bytes.
 IP (Internet Protocol) is the part that takes care of addressing the
packets and directs them thru their proper itineraries.

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Internet backbone
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Internet backbone can be compared to human backbone or
spine because it connects every internet host user to other
users like human backbone connect to every organ and cell of
the human body.
This backbone comprises all fast and broad band networks and
connections owned by major telecommunication companies
(AT&T, Spirit, French telecom, Finn telecom, etc…) all around
the world including:
Under ocean cables installed by submarines and known as submarine
cables that link most continents.
 Satellites owned and operated by large telecommunications
companies because the private sector took over in 1994.
 Ground high speed telecommunication and networking infrastructure
including wired and wireless infrastructure.

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Internet status
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Nobody own the Internet, however big telecommunication
companies own parts of the Internet backbone and make profit
by charging use fees so Internet providers can be divided into
3 tiers:
Tier 1: comprises huge ISP (Internet Service Provider) companies that
don’t need to pay anything to access all nodes of the Internet. Qwest,
AT&T, Verizon, sprint, French telecom, Finn telecom etc…
 Tier 2: comprises ISP companies that need to pay for some access
from Tier 1 companies.
 Tier 3: Comprises ISP companies that lease Internet access from Tier
1 or Tier 2 companies provide services to subscribers and don’t own
connections by themselves.
 Tier 1, Tier 2 and Tier 3 companies are all Internet service providers
(ISP)s and that’s why the quality of Internet service is normally better
with Tier 1 companies then Tier 2 then Tier 3.
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Internet access
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Five most important characteristics of Internet access are:
 Reliability: Connection is available when needed without
unexpected interruption due to coverage and weather
 Speed: Download speed and upload speed in Mbps.
 Cost should be reasonable and justified.
 Customer satisfaction oriented help and assistance service
 Free array of popular general information
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News
Weather
Gaming
Travel and entertainment.
ISP (Internet Service Provider) provides a modem (modulator
demodulator) that is able to accommodate all services provided.
Dr. Nazih Abdallah - Modern business computer
Internet access methods
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Dial-up connection: The first used method of access
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DSL (Digital Subscriber Line)
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Always On Internet service
Provided by telephone companies and uses telephone lines.
Because of switching technology provided by the ISP, you can use both the telephone and the Internet simultaneously.
Fast Internet that may go up to 6 Mbps.
Price is reasonable but much higher than dial-up connection service
Cable TV: provides the connection as part of a package that includes TV channels and possible more services like Internet
telephone
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Host must dial a number and wait until getting access.
Very slow access impossible to deal with multimedia because it can only handle up to 56 Kbps
Uses telephone line so you cannot use the telephone and access the Internet simultaneously (one service at a time)
Service is ON only after you dial and be lucky to get connected
Still used in some rural areas where there is no fast Internet yet.
The least expensive service of all.
Always ON connection
A splitter modem is provided by the CTV provider that routes TV channels to the TV and Internet service to the computer or the
wireless router if you want to install a WI-FI network.
You can watch TV and access Internet and its services simultaneously.
Very fast connection up to 8 Mbps and may reach up to 50 Mbps in case businesses want speed beyond what is offered for the public.
Slightly higher cost than DSL
Very reliable (not affected by weather condition.
Satellite access: direct satellite access is provided by many companies that operate and manage satellites like HughesNet,
My Blue Dish and Wild blue in the USA.
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Provide fast Internet in rural areas where only dial-up connection or no connection at all is available.
Always ON connection
Speed may go up to 18 Mbps.
Very reliable Internet access
Most expensive Internet service.
Dr. Nazih Abdallah - Modern business computer
VPN (Virtual Private Network)
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Very important business network that use client server topology
May have partly installed local structure.
 Operates using public networks (mainly the Internet) to exchange
private data and make private communications
 To enforce and enhance communication security a protocol known
as “Tunneling” protocol is used.
 Tunneling protocol usually does the following:
 Authenticate the client requesting communication to the VPN
 Create a secured tunnel (pathway).
 Complete and control the communication thru that tunnel.
 VPN is used by businesses to create connection possibilities for
their Intranet and Extranet as we will see below.

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Intranet
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 Internetwork of many private networks in a company
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designed to accommodate teamwork and enhance
communication and file sharing in a company
Uses the Internet protocol TCP/IP
Hi security network in a business.
Only authorized executives, managers and employees can
access it (no outsiders allowed in)
An Intranet consists of:
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Internal e-mail system
Database loaded with important information and news about the
company and its working environment.
Websites and some other services as needed.
Secured and firewalled Internet access
VPN connection to support remote access for company’s staff.
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Extranet
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 Internetwork like Intranet but with strictly
controlled outside access
 Use VPN (Virtual Private Network) to connect with
another network in a different organization.
 Extranets are widely used by medium and large
companies because of the simplicity and convenience
they add to business – customer relationship and
easiness of communication between businesses.
Dr. Nazih Abdallah - Modern business computer
VAN (Value – Added Network)
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 considered as a competitor to the post office for business
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documents and file exchange between businesses.
Privately owned highly secured network using private
communication media
Provides specific services known as VAN services like legal service
or translation or accessing special database.
Handles electronic mail and file transfer between businesses like
EDI (Electronic Data Interchange) transactions.
Businesses lease lines to connect to the network and need to install
specific software for this purpose.
Internet replaced many VANs lately and successfully introduced
itself as much efficient and economic tool to replace the VAN.
VAN use remains popular between businesses that are seeking high
security level when exchanging files
Dr. Nazih Abdallah - Modern business computer
Search Engine
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 Search engine: like Google help the browser in finding
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website addresses for clients
Software tool that finds related documents from diverse
Internet sources using keywords
Scour the Web with bots (automated programs) called
spiders: Crawling
Meta search engine allows users to run keyword searches
on several search engines at once
Synchronous communication: People communicate
in real time exchanging thoughts in a flowing
conversation
Asynchronous communication: Allows participants
to leave messages
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Chat & Instant messaging
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 Chat and Instant messaging
 Synchronous one-to-one text-based communication over the Internet
 Instant messaging software supports the following services
 Instant messages
 Chat
 Nudges, animated winks, and graphics
 Web links
 Image, sounds
 Files and file sharing
 Talk
 Streaming content
 Chat: Synchronous text messaging between two or more users
 Channels or chat rooms: Topic-related forums
 Virtual chat: Provides a virtual world to chat and interaction with
others: Avatar provides 3D representation of yourself in the virtual
world
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Other web services
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 Text messaging (Short Message Service or
SMS): Method for sending short messages between
cell phones: Not longer than 160 characters.
 Web Logs (Blogs): Sites created to express the
views and opinions of an individual
 Originally used as online journals, but as they
became more mainstream, tools were developed to
aid users in creating blogs and RSS reader is a tool
used to subscribe to a blog
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Viruses and Worms
 Virus
Program that attaches itself to a file
Spreads to other files, and delivers a destructive action called
a payload
 Time bomb: Virus that delivers payload on a specific time
(birthday of celebrity, anniversary of an incident, etc…)
 Logic bomb: delivers payload on specific conditions (click a
link, open a file, boot, etc…)
 Trojan horses
 Appear to be harmless programs
 When they run, they install programs on the computer that
can be harmful
 Backdoor Trojans open ports on the computer for hackers
access.
 Worm : Acts as a free agent, replicating itself numerous times in
an effort to overwhelm systems causing denial of service attack
on a network (traffic jam).
 War driving: Driving through neighborhoods with a wireless
notebook or handheld computer looking for unsecured Wi-Fi
networks.
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Defending Against Viruses and Worms
 Antivirus software uses several techniques to:
 Find viruses: 2 steps:
Detect the virus presence using Checksum of the file.
 Checksum is the actual number of bytes in the file
saved by the AV software and compared to the new
number. If the numbers are different there should be a
virus.
 Find the identity of the virus by comparing its signature
to the available list of virus signatures.
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AV then removes them if possible or quarantine them until
they can be removed.
Keep additional viruses from infecting the system
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Information Security and Vulnerability
 Organizational information
 Compromised information can lead to
Loss of market share
 Business failure
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 Business intelligence
 Process of gathering information in the pursuit of business
advantage
 Competitive intelligence
 Concerned with information about competitors
 Counterintelligence
 Concerned with protecting your own information from
access by your competitors
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National and Global Security
 Cyber-terrorism
 Uses attacks over the Internet to intimidate or harm a
population
 United States Computer Emergency Readiness
Team (US-CERT)
Monitors the security of US networks and the Internet
 Responds to attacks
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 National Strategy to Secure Cyberspace
 Prevent cyber-attacks against US infrastructure
 Reduce national vulnerability to cyber-rattack
 Minimize damage and recovery time
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Threats to Information Security:
Hackers, Crackers, Intruders, and Attackers
 System penetration: Someone subverting the security of a system without
authorization
 Hackers, crackers, intruders, and attackers
 Hackers convene every year in Las Vegas the convention is nicknamed HOPE
(Hackers On Planet Earth): Media, businesses and government specialists attend
the convention to be aware of new hacking and security advances .
 White-hat hacker: No criminal intention, Don’t make money
 THEY MAY BE HIRED BY BUSINESSES TO CHECK AND
CONSOLIDATE THEIR NETWORK SECURITY (in this case they
make legally money).
 Black-hat hacker: Criminal intention, make money (cracker).
 Gray-hat hacker: Can be either one
 Script kiddie: Try to gain access to a network using scripts of other hackers.
 Computer forensics
 Process of examining computer equipment to determine if it has been used for
illegal, unauthorized, or unusual activities
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Machine-Level Security
 Common forms of authentication
 Something you know
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Something you have
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Password or personal identification number (PIN)
ID cards, smartcards, badges, keys,
Something about you
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Unique physical characteristics such as fingerprints
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ID Devices and Biometrics
 Biometrics
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The science and technology of authentication by scanning and
measuring a person’s unique physical features
 Facial pattern recognition
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Uses mathematical technique to measure the distances
between 128 points on the face
 Retinal scanning
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Analyzes the pattern of blood vessels at the back of the eye
 Fingerprint scan
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Increasingly common method for access to secure areas,
logging onto computers, and even validating credit
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Encrypting Stored Data
 Encryption
 Uses high-level mathematical functions and computer
algorithms to encode data
 Files
 Can be encrypted “on the fly” as they are being saved, and
decrypted as they are opened
 Encryption and decryption
 Tend to slow down computer slightly when opening and saving
files
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Backing up Data Files
 Backup software typically provides the following
options
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Select the files and folders you wish to back up
Choose the location to store the archive file (back-up location
must be away from actual system location)
Choose whether to back up all files (a full backup), or just
those that have changed since the last backup (an incremental
backup)
 Mirroring
 Creating a copy of the file system or a portion of it
 Real-time mirroring: As files are saved, they are automatically
updated in the mirrored back-up copy.
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Scams, Spam, Fraud, and Hoaxes
 Virus hoaxes
 E-mail that warns of a virus that doesn’t exist
 In some cases, just a nuisance, but they can cause
great harm in other cases
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Hoax may ask you to delete a “virus” file that is actually an
uninfected, important system file
Deleting such a file may make your computer unusable
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Scams, Spam, Fraud, and Hoaxes
 Defending against scams, spam, fraud, and hoaxes
 Awareness and common sense
 Do not click links sent by e-mail
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Type URLs directly into the browser
Examine Web addresses to make sure they are legitimate
Do not believe virus alerts sent through e-mail unless they
come from a reputable source
Use spam filters
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