Chapter7 The Web and E-mail1 Is The Web and The Internet the same thing? No The Internet is the networking infrastructure –Hardware and software that connects.

Chapter7 The Web and E-mail 1

• Is The Web and The Internet the same thing?

• No

• The Internet is the networking infrastructure– Hardware and software that connects host

machines and enables communication• Hardware includes:

– Links such as cables and wireless channels– Nodes such as user computers, routers, and gateways

• Software includes TCP and IP protocols

The Web and E-mail

What is the Web?

• The web (World Wide Web) is a collection of data (audio, video, text, etc.) typically connected through hyperlinks

• The web is hosted by servers on the Internet – Web sites are accessed using a protocol called

HTTP (HyperText Transport Protocol)

• The Internet hosts other protocols– ftp (try frp://ftp.giga.net.tw for example)


Web Basics

• What is a Web site?– Collection of related and formatted information

• Formatted by html (hypertext media language) and its derivatives (i.e., xml)

– Hypertext are data linked together by logical relationships

– Accessed by web browsers (client software)– Controlled by web servers (computers) that

respond to client requests– Sites are composed of web pages


URL• Universal Resource Locator

– Each web page has a unique URL– http://www.fdu.edu – FDU’s domain address– https://webmail.fdu.edu

• Secured http (SSL used for encryption)

– http://alpha.fdu.edu/~levine/survey/index.html• http: web protocol standard

• alpha.fdu.edu - fdu’s web server

• levine and survey – subdirectories (folders)

• index.html -- default web page


HTML, JavaScript, XML

• HTML – formatting & linking instructions– Use JavaScript to allow client interaction– HTML5 is the newest standard

• XML – data relationships, dynamic pages

• HTML format can be seen by “view source”

• Compare source code to web page


Steps in an http data transfer• Client inserts URL in browser address field

– Client’s browser, TCP/IP software and Ethernet or wireless LAN card set up a connection with server at requested URL

• Client software opens a socket (port is assigned by OS) to connect to “listening” port (80, 443) at server

– Client clicks on a link (get command) for downloading data to its machine

– Server sends requested page.– Client and server disconnect


Web surfing errors

• http status code 404 is returned if the site/ page is invalid

• Broken link is seen if a graphic does not exist or client does not have correct access rights

• Sometimes the server is busy or has crashed and you will get a message that server may be busy or temporarily down


Browsers• Internet Explorer, Mozilla Firefox, Google

Chrome, Apple Safari, Opera– Netscape, first commercial browser with GUI,

was used by FDU from 1994 – 2009• Based on Mosaic

– By 1997 Internet Explorer, bundled with Windows, replaced Netscape as top browser

– Firefox and Chrome are open source; include advanced security features


Browsers and file formats• Browsers need to be updated to handle new

file formats, patches as they are introduced

• Sometimes additional software is needed– Adobe Reader (free software) handles PDF

files– Adobe’s flash software for Flash (discontinued)– Explorer has ActiveX component tags to

specify additional (helper) applications


Web cache• Pages that you download are stored in your

local browser cache for days or weeks– Cache is used to make retrieval much faster in case you

reference the site again

– If you make changes on a web page, you are likely to view the old copy. Try the reset arrows

– If you browse on a public computer, others can find these pages

• Use Explorer/tools/delete browsing history

• Explorer/tools/Internet options/delete temporary files

– Caches are searched by forensic personnelChapter7 The Web and E-mail 10

What are cookies?

• Web servers store small sets of data in text files on client hard disk for later use– http is “stateless” – eases exchanging information

• Place items in Shopping cart one at a time

– Servers use cookies to monitor client behavior

• Pages visited

• Items purchased

– Cookies help collect information to facilitate targeting clients with ads tailored to them

– Keep client information for later visits


How to write html code?• Use HTML conversion utilities

– Results may need to be changed

– Might be difficult to alter

• On-line page authoring tools are frequently offered by ISPs that host your web pages– Very limited templates

• Web authoring software– Adobe Dreamweaver, SeaMonkey (open source)


Web pages with text editors

• Learn to write html code– Use a text editor for the framework– Images, video, etc. are inserted separately

through links and tabs

<video>


Basic HTML code<html> or <!DOCTYPE HTML -->

<head>

<title> My web page </title>

</head>

<body>

 This is my first web page 

 This is my second line 

</body>

</html>


Writing html script

• Open notepad

• Write your code

• Save as • All files

• With htm extension

• Place in a location you recognize

• Keep both the directory and notepad open

• Execute the file; change notepad and redoChapter7 The Web and E-mail 15

Links to pages and images with HTML

<img src =“picture.gif” > where picture.gif is in the same directory as your file

In general, you must give path to the image.

<a href="environments/index.html">

Information on the Unix and Ada environments at FDU</a>


HTML scripts• Scripts allow pages to react to user input

– “interactive”

• Script forms allow users to enter data – Can limit the values that are entered

• Client side scripts are typically written in JavaScript

• Server side scripts are typically written in Perl, PHP, JAVA, C#


Search Engines

• Search engines include:– Google; bing; yahoo; ask; altavista – They are automated tools– They search huge data bases

• Some search engines are human-powered– www.mahlo.com; www.chacha.com

• Screened by human experts

• Many sites have humans answering queriesChapter7 The Web and E-mail 18

Process used by search engines

• Web crawlers (spiders) “methodically” visit sites and download pages for analysis– They start at well known sites; follow site links– Algorithms eliminate loops, self references

• Different search engines visit somewhat different sets of sites

• Only about 20% of pages are “seen”– Password protected; dynamically created, etc.


Search engine indexing

• Database contains lists of pages based on key words– Web designers try to ensure that key words are

placed near the top of the document• Old comic books. Choose some key words.

– Comics

– Comic book

– Superhero

– Batman, Superman, Wonder Woman, Captain America


Ranking and placement

• Search engines may sell “sponsored links”– Top rows; right column

• Link popularity – links from and to popular sites

• High rating by # of keywords found during indexing– Page author may “stuff” popular keywords (e.g.

sex) even though the page is not about sexChapter7 The Web and E-mail 21

Query processing

• (keyword) Queries typically produce many thousands of results – how to narrow this?– Common words (and, the, if) are ignored– Variations of your keywords are also searched

• Appending * specifies searching for variations

– Exact phrase should be entered in quotes– Near operator to specify that keywords should

be adjacent, such as library NEAR/15 congress


Privacy and search engines

• Search engines keep information of user queries (perhaps for limited time??)

• U.S. Department of Justice has requested query databases, specifically for child pornography

• AOL released a database on-line of 20 millions queries in 2006– User ID, search keywords; date and time


Search engines and user IDs

• Search engines assign user IDs to computers during search– User ID remains in cookies on your computer

• You can delete all cookies after each session

• You can block cookies from specific sites


Copying web material• Obviously, sites frequently copy words from

each other without reference– For homework or research it is plagiarism

• Words and pictures can be copied for educational use (copy/paste option)– Must cite the reference– Use URL at the top of the page; title, author, date

if available

• Check link for terms of use Chapter7 The Web and E-mail 25

E-Commerce

• E-commerce uses the Web and Internet for transactions and information– Businesses increase profit margin by cutting

costs (estimated that on-line methods cost about 10% of methods that require human interaction)

• Many telephone services today are automated


Advertising on the Web

• Banner ads embedded in (top of) web pages

• Hover ads overlay web pages – client must specifically close them

• Pop-up ads appears in a separate window when client connects to a site– Clicking on any of these connects client to

advertiser’s web site• Hosting merchant is paid for click-through rate


Blocking and deleting cookies• Internet Explorer

– Tools/ Internet Options/ Privacy• Pop-up blocker – turn-on (block most pop-ups)

• Advanced Privacy Settings/override automatic» First-party cookies – accept/block/prompt choice

» Third-party cookies – block

– Tools/Internet Options/General• Delete browsing history on exit

– Tools/Internet Options/Advanced/security/

– empty temp Internet files folder when browser is closed


E-mail• Anyone can use e-mail if they have access

to the web and have an e-mail account– Yahoo, google, client’s ISP provide accounts

• E-mail messaging includes– cc– Forwarding, reply– Group emails– Attachments (MIME is an Internet protocol to

encapsulate all types of data as ASCII)Chapter7 The Web and E-mail 29

Email formatting option

• Email software may allow Word or HTML formatting– Email can then contain graphics and other types

of non-ASCII formats– Exposes receiver to malware– Word and Excel have embedded Macros


Netiquette for e-mail• Include meaningful subject line

– Don’t reply with previous subject line• Use upper and lower case letters

– Reserve all upper case for SHOUTING• Check spelling• Don’t “reply to all” unless you need that• Notify recipients of previous emails if you

discover you have a virus.


E-mail and privacy

• FBI uses commercial sniffers to monitor emails of suspected criminals & others?– USA Patriot Act 2001– Software scans ALL emails passing through the

ISP, not only the suspected terrorist

• Employer has legal access to your email– “If legitimate business need exists”

• Your email may be forwarded to others


E-mail and privacy (cont.)

• It is easy for you to accidentally send an email to the wrong address. Would an ISP do that? I doubt it.

• ISPs store emails even if they have been deleted.

• Schools store student email messages

• “Think of your email as a postcard.”


Phishing and Pharming• Phishing is a scam that uses fraudulent links

in emails or web sites that ask for confidential information– Web site typically looks legitimate– Move cursor over link to see real URL

• Check that URL is EXACTLY the same as required

• Pharming poisons the DNS so that URL is translated to a fake IP address – the URL displayed will be correct; site will not be


Packet sniffer & Spam• Assume no encryption is used, a sniffer can

“see” and translate all traffic– Steal credit card numbers

• Spam is unsolicited electronic mail – may include requests for email passwords, etc.

• Security protocols to encrypt your data include SSL, TLS, HTTPS

• Spam filters to block spam

Chapter7 The Web and E-mail1 Is The Web and The Internet the same thing? No The Internet is the networking infrastructure –Hardware and software that connects.

Documents

web basics

web world wide web

web pages chapter7

web browsers client

internet web sites

web protocol standard

web servers computers

default web page chapter7