Internet
What is Internet
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Internet is a computer network made up of
millions of networks worldwide.
No one knows exactly how many computers
are connected to the Internet.
It is certain, however, that these number in
the millions and are increasing at a rapid
rate.
No one is in charge of the Internet.
What is Internet
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There are organizations which develop
technical aspects of this network and
set standards for creating applications
on it, but no governing body is in
control.
The Internet backbone, through which
Internet traffic flows, is owned by
private companies.
What is Internet
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All computers on the Internet communicate
with one another using the Transmission
Control Protocol/Internet Protocol suite,
abbreviated to TCP/IP.
Computers on the Internet use a client/server
architecture.
The remote server machine provides files and
services to the user's local client machine.
Software can be installed on a client
computer to take advantage of the latest
access technology.
Services accessible through
Internet
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Electronic mail
File transfer
Vast information resources
Interest group membership
Interactive collaboration
Multimedia displays
Real-time broadcasting
Shopping opportunities
Breaking news, and much more.
COMPONENTS OF THE
INTERNET
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World Wide Web
E-mail
Telnet
FTP
E-mail Discussion Groups
USENET News
Chat etc.
World Wide Web
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The World Wide Web is a system of Internet
servers that supports hypertext to access
several Internet protocols on a single
interface.
The World Wide Web is often abbreviated as
the Web or WWW.
The World Wide Web was developed in 1989
by Tim Berners-Lee of the European Particle
Physics Lab (CERN) in Switzerland
World Wide Web
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Almost every protocol type available on the
Internet is accessible on the Web. They are
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E-mail (Simple Mail Transport Protocol or SMTP) Distributes electronic messages and files to one
or more electronic mailboxes
Telnet (Telnet Protocol)
Facilitates login to a computer host to execute
commands
FTP (File Transfer Protocol)
Transfers text or binary files between an FTP
server and client
World Wide Web
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Usenet (Network News Transfer Protocol
or NNTP) - Distributes Usenet news articles
derived from topical discussions on
newsgroups
HTTP (Hypertext Transfer Protocol)
Transmits hypertext over networks. This is
the protocol of the WWW.
The World Wide Web provides a single
interface for accessing all these protocols.
World Wide Web
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How can we access World Wide Web
(Web)
Using one of the Web Browsers
What's in a Web browser?
A Web browser contains the basic
software you need in order to
 Find
 Retrieve
 View and
 Send
information over the Internet.
What's in a Web browser?
This includes software that lets you:
 Send and receive electronic-mail (or email) messages worldwide nearly
instantaneously.
 Read messages from newsgroups (or
forums) about thousands of topics in
which users share information and
opinions.
 Browse the World Wide Web (or Web)
where you can find a rich variety of
text, graphics, and interactive
information.
What is a URL?
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URL stands for Uniform Resource Locator
The URL specifies the Internet address of a file
stored on a host computer connected to the
Internet.
Every file on the Internet, no matter what its
access protocol, has a unique URL.
Web software programs use the URL to retrieve
the file from the host computer and the directory
in which it resides.
This file is then displayed on the monitor
connected to the user's local machine.
What is a URL?
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URLs are translated into numeric addresses
using the Internet Domain Name System
(DNS).
The numeric address is actually the "real"
URL.
Since numeric strings are difficult for humans
to use, alphneumeric addresses are employed
by end users.
Once the translation is made, the Web server
can send the requested page to the user's
Web browser.
Anatomy of a URL
Usually it consists of four parts:
 Protocol
 Server (or domain)
 Path and
 Filename.
Sometimes there's no path or
filename.
Anatomy of a URL
Here's an example:
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http://www.microsoft.com/windows/default.asp
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http is the protocol
www.microsoft.com is the server
windows/ is the path
default.asp is the filename
CGI (Common Gateway
Interface)
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It refers to a specification by which programs
can communicate with a Web server.
A CGI program, or script, is any program
designed to accept and return data that
conforms to the CGI specification.
The program can be written in any
programming language, including C, Perl, and
Visual Basic Script.
Search engines: Finding the
needle in the haystack
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A search engine is a service that
indexes, organizes, and often rates and
reviews Web sites. Different search
engines work in different ways:
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Some rely on people to maintain a catalog
of Web sites or pages.
Some use software to identify key
information on sites across the Internet.
Some combine both types of service.
Search engines
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Some Common Search Engines:
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MSN
Yahoo
Lycos
AltaVista
WebCrawler
InfoSeek
Snap
Excite
All About E-mail
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To send and receive electronicmail messages, or e-mail, over the
Internet and to organize your
messages, you need
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An e-mail account through an
Internet service provider (ISP) or
online service provider.
An e-mail client—e-mail software for
your computer
E-mail Clients
Microsoft Outlook
 Microsoft Outlook Express
 Netscape Messenger
 Eudora
Or
Some Web based Email Client
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E-mail terminology
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There are many acronyms associated with
e-mail:
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SMTP—simple mail transfer protocol; the
standard rules that many e-mail clients use to
handle outgoing e-mail messages.
POP3—postoffice protocol version 3; the
standard rules that many e-mail clients use to
handle incoming e-mail messages.
MIME—multipurpose Internet mail extensions;
a format for turning an e-mail attachment,
such as a Microsoft Word file, into ASCII text
so it can be sent from one e-mail account to
another.
Internet Threats & Security
Since Internet is accessible to many it is
also prone to attacks from hackers. The
threats to the Inter are as follows:
• Disclosure
• Masquerade (Spoofing)
• Unauthorised Access
• Loss of Integrity
• Denial of Service
Internet Threats & Security
Theft of Service & Resources:
Internet is used as a channel for delivery of
service. Hence, unauthorised access to the
services is a theft.
The impacts due to threats are:
• Loss of trade secrets
• Information is lost (Critical data, proprietary
info, Contracts)
• Increased cost of security systems
Internet Threats & Security
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Loss of reputation and goodwill
It is very costly to correct and recover
information
Contractual commitments are not met
properly
Loss of Income
Legal and regulatory non compliance
Internet Threats & Security
Internet Security Controls:
 Data Security & Controls
 Firewall Security
 Corporate Internet Policy & procedures
 Data Encryption