Objectives
• Computer Networks
• Web Technology
• Search Engines
• E-commerce
• E-mail
• Web and E-mail Security

Computer networks
• A collection of computing devices connected in
order to communicate and share resources.
• Connections between computing devices can be
physical using wires or cables or wireless using radio
waves or infrared signals
• Node (host)
– Any device on a network
• Data transfer rate (bandwidth)
– The speed with which data is moved from one place to
another on a network

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Computer networks
Computer networks have opened up an entire
frontier in the world of computing called the
client/server model

Computer networks
• Protocol
– A set of rules that defines how data is formatted and processed
on a network; i.e., rules that allow client/server interaction.
• File server
– A computer that stores and manages files for multiple users on
a network.
• Web server
– A computer dedicated to responding to requests (from the
browser client) for web pages.
Types of Networks
Local-area network (LAN)
A network that connects a relatively small number
of machines in a relatively close geographical area
– Ring topology connects all nodes in a closed loop
on which messages travel in one direction
– Star topology centers around one node to which
all others are connected and through which all
messages are sent
– Bus topology nodes are connected to a single
communication line that carries messages in both
directions

Types of Networks

Types of Networks
• Wide-area network (WAN)
A network that connects local-area networks over a
potentially large geographic distance
• Metropolitan-area network (MAN)
The communication infrastructures that have been
developed in and around large cities
• Gateway
One particular set up to handle all communication
going between that LAN and other networks

Types of Networks
Local-area networks connected across a distance to create a wide-area network

Types of Networks
Internet
A wide area network that spans the planet

Packet Switching
Packet
A unit of data sent across a network
Router
A network device that directs a packet between networks
toward its final destination
Packet switching
Messages are divided into fixed-sized, numbered packets;
packets are individually routed to their destination, then
reassembled

Packet Switching

Open Systems
• Proprietary system
A system that uses technologies kept private by a
particular commercial vendor.
• Interoperability
The ability of software and hardware on multiple
machines and from multiple commercial vendors to
communicate.
• Open systems
Systems based on a common model of network
architecture and a suite of protocols used in its
implementation.

Open Systems
Open Systems
Interconnection Reference
Model
A seven-layer logical break
down of network interaction to
facilitate communication
standards
Each layer deals with a
particular aspect of network
communication

Network Protocols
• Network protocols are layered such that each
one relies on the protocols that underlie it
• Sometimes referred to as a protocol stack

TCP/IP
Transmission Control Protocol (TCP)
Software that breaks messages into packets, hands
them off to the IP software for delivery, and then
orders and reassembles the packets at their
destination
Internet Protocol (IP)
Software that deals with the routing of packets
through the maze of interconnected networks to
their final destination

TCP/IP
User Datagram Protocol (UDP)
An alternative to TCP that is faster but less reliable
Ping
A program used to test whether a particular
network computer is active and reachable
Traceroute
A program that shows the route a packet takes
across the Internet

High-Level Protocols
Other protocols build on TCP/IP protocol suite
Simple Mail Transfer Protocol (SMTP) used to specify
transfer of electronic mail
File Transfer Protocol (FTP) allows a user to transfer
files to and from another computer
Telnet used to log onto one computer from another
Hyper Text Transfer Protocol (http) allows exchange
of Web documents

High-Level Protocols
Port
A numeric designation
that corresponds to a
particular high-level
protocol

MIME Types
MIME type
• A standard for defining the format of files that
are included as email attachments or on websites
– What does MIME stand for?
Multipurpose Internet Mail Extension

Network Addresses
Hostname
A name made up of words separated by dots that
uniquely identifies a computer on the Internet
IP address
An address made up of four one-byte numeric
values separated by dots that uniquely identifies a
computer on the Internet

Web Basics
• The Web is a collection of
document, image, video, and
sound files
– Web 2.0
– Web 3.0
• A Web site contains a
collection of related
information

Web Basics
• A Web server accepts requests from browsers
• A Web page is the product or output of one or
more Web-based files displayed in a format
similar to a page in a book
• A Web browser is client software that displays
Web page elements and handles links between
pages
• Every Web page has a unique address called a
URL

HTML
• Set of specifications for creating documents that
a browser can display as a Web page
• Markup language
• HTML tags
• HTML 5
• XHTML
• HTML document

HTTP

Web Browsers
• Popular browsers:
– Internet Explorer
– Mozilla Firefox
– Apple Safari
– Google Chrome
• It is a good idea to
upgrade when a new
version of your
browser becomes
available

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Cookies
• Small chunk of data generated by a Web server
and stored in a text file on computer’s hard disk
– Fix problems caused by HTTP’s stateless protocol
– Relatively safe
• Your computer does not have to accept cookies

Web Page Authoring
• HTML conversion utility
• Online Web authoring tools
• Web authoring software
– Adobe Dreamweaver
• Text editor

Search Engine Basics
• A Web search engine is a program designed to
help people locate information on the Web by
formulating simple keyword queries

Search Engine Basics
• A Web crawler is a computer program that is automated to
methodically visit Web sites
• A search engine indexer is software that pulls keywords from
a Web page and stores them in an index database
• A search engine’s query processor looks for your search
terms in search engine’s indexed database and returns a list
of relevant Web sites
• Link popularity is measured by quantity and quality of links
from one Web page to others
• A meta keyword is entered into a header section of a Web
page when it is created and is supposed to describe the
page contents
– Keyword stuffing

Formulating Searches
• Most search engines work with keyword queries in
which you enter one or more words, called search
terms

Formulating Searches
• A search operator is a word or symbol that
describes a relationship between search terms
and thereby helps you create a more focused
query

E-commerce Basics
• Business transactions conducted
electronically over a computer network
– B2C (business-to-consumer)
– C2C (consumer-to-consumer)
– B2B (business-to-business)
– B2G (business-to-government)

E-commerce Basics
• Enhances traditional business models
• Styles of online advertisements
– Banner ad
– Hover ad
– Pop-up ad
• Click-through rate
• Ad-blocking software prevents ads
from appearing on screens

E-commerce Site Technology
• E-commerce offers some unique advantages
over brick-and-mortar stores and mail-order
catalogs
– Easily search for merchandise
– Easily compare prices and products
• Two popular models
– B2C
– C2C

E-commerce Site Technology

E-commerce Site Technology

E-commerce Site Technology
• At C2C auction and online classified advertising
e-commerce sites, consumers offer goods and
services to other consumers
• C2C sites are hosted by an e-commerce provider
such as eBay, Tonaton, OXL

Online Payment
• The most popular ways to make online payments
include submitting your credit card number
directly to a merchant and using a third-party
payment service such as PayPal
• Online shoppers are justifiably worried that
personal information and credit card numbers
supplied in the course of an e-commerce
transaction might be hijacked and used
inappropriately

Online Payment
• A secure connection encrypts the data
transmitted between your computer and a Web
site
• SSL (Secure Sockets Layer)
• TLS (Transport Layer Security)
• HTTPS (Hypertext Transfer Protocol Secure)

Online Payment

• Person-to-person payments are an alternative to
credit cards
– The payment service is the only entity that sees your
credit card number
E-Mail Overview
• An e-mail message is an electronic document
transmitted over a computer network.
• The computers and software that provide e-mail
services form an e-mail system.
• An e-mail server acts as a central post office for a
group of people
• A message header is divided into fields that
contain the sender’s e-mail address, the
recipient’s address, a subject line, and the date
and time the message was written

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E-Mail Overview
• To use an e-mail system, you need:
– Internet connection
– E-mail account
– E-mail software
• E-mail client
software
• Webmail

Local E-mail
• When you use local e-mail, an e-mail server
stores your incoming messages until you launch
your e-mail client and get your mail
– Based on store-and-forward technology
• E-mail protocols
– POP3
• (Post Office Protocol 3)
– IMAP
• (Internet Message Access Protocol)
– SMTP
• (Simple Mail Transfer Protocol)
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E-Mail Attachments
• E-mail attachments are files that travel with an email
message
– E-mail software converts e-mail attachments using a conversion
process called MIME
• When working with attachments, keep the
following points in mind:
– Don’t send huge attachments
– Explain all attachments
– Don’t open suspicious attachments
– You can save attachments
– You might have to download a plug-in or player
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Netiquette
46
Web and E-mail Security
• Cookie Exploits
• Spam
• Phishing
• Fake Sites 

Cookie Exploits
• An ad-serving cookie can select and display ads
that might interest you

Cookie Exploits
• A Flash cookie, also called a local shared object,
is the Flash equivalent of a conventional Web
cookie
• A Web bug or clear GIF is typically a 1x1 pixel
graphic embedded in a Web page or e-mail
message. It is almost invisible due to its size and
is designed to track who’s reading the Web page
or e-mail message
• Antispyware is a type of security software
designed to identify and neutralize Web bugs,
ad-serving cookies, and other spyware

Cookie Exploits

• Individuals who prefer not to leave a trail of their Internet activities surf through an anonymous proxy service, which uses an intermediary, or proxy, server to relay Webpage requests aftermasking the originating IP address
 
Spam
• Spam is unwanted electronic junk mail about
medical products, low-cost loans, and fake
software upgrades that arrive in your online
mailbox
• Spam has turned into another major hacking
tool for cybercriminals
• A spam filter is a type of utility software that
captures unsolicited e-mail messages before
they reach your inbox

Phishing
• Phishing is an e-mail based scam designed to
persuade you to reveal confidential information,
such as your bank account number or Social
Security number
• If you don’t want to become a phishing victim,
be suspicious of e-mail messages that
supposedly come from banks, ISPs, online
payment services, operating system publishers,
and online merchants

Fake Sites
• A fake Web site looks
legitimate, but has been
created by a third party to
be a very clever replica of
a legitimate Web site
• Pharming is an exploit
that redirects users to
fake sites by poisoning a
domain name server with
a false IP address
• Pharming is more
surreptitious and tougher
to detect than most other
hacker schemes

Summary
• Networks and types of networks
• Networking and web protocols
• Web
• Email
• Email and Web security

Quick Review
• http://www.cnn.com is an example of a URL.
• The Web uses WEP as its main protocol
• If your browser can’t open PDF files, you can
download the Adobe Reader plug-in.
• The Web uses cookies because HTTP is stateless.
• [/ left] is an example of an HTML tag.

Quick Review
• A Web crawler is type of virus that affects
cookies.
• Keyword stuffing is a technique for collecting
user IDs from Web site logins.
• Most e-commerce shopping carts use cookies to
keep track of the items you are purchasing.

Quick Review
• Secure connections typically begin with https.
• POP, IMAP, and SMTP are Web page protocols.
• E-mail attachments are converted with MIME
into ASCII code.
• Blocking third-party cookies helps eliminate Web
bugs.

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