04/18/23 Cookies 1

What are Cookies?

04/18/23 Cookies 2

How did they do that?

04/18/23 Cookies 3

Sites that know you... Just a few common examples:

my.yahoo.com www.amazon.com

Each time I return to these sites, they remember who I am. Yahoo remembers my news, bookmarks, etc. Amazon.com remembers what books I have

browsed and makes recommendations. How do they do that?

04/18/23 Cookies 4

What is a Cookie? Small piece of data generated by a web

server, stored on the client’s hard drive.

Controversial, as it enables web sites to track web users and their habits (more later…)

04/18/23 Cookies 5

Tracking Unique Visitors Step 1: Person A requests home page for

amazon.com Step 2: amazon.com Web Server generates a

new unique ID. Step 3: Server returns home page plus a

cookie set to the unique ID. Step 4: Each time Person A returns to

amazon.com, the browser automatically sends the cookie along with web page requested.

04/18/23 Cookies 6

Cookie Conversation

Browser Server

Give me the home page!

Here’s the home page plusa cookie.

Now, give me the news page(cookie is sent automatically)

I’ve seen you before… Here’sthe news page.

04/18/23 Cookies 7

Cookie Notes Created in 1994 for Netscape 1.1 Cookies cannot be larger than 4K No domain (netscape.com, microsoft.com)

can have more than 20 cookies. Cookies stay on your machine until:

they automatically expire they are explicitly deleted

Cookies work the same on all browsers. No cross-browser problems here!

04/18/23 Cookies 8

Magical Cookies The term cookie comes from an old

programming hack, called Magical Cookies.

If a programmer couldn’t make two parts of a program communicate, she would create a “magical cookie”, a small text file containing data to transfer between program parts.

04/18/23 Cookies 9

Why use Cookies? Tracking unique visitors Creating personalized web sites Shopping Carts Tracking users across your site:

e.g. do users that visit your sports news page also visit your sports store?

04/18/23 Cookies 10

Cookie Anatomy

04/18/23 Cookies 11

Cookie Anatomy Version 0 specifies six cookie parts:

Name Domain Path Expires Secure

04/18/23 Cookies 12

Managing Cookies

04/18/23 Cookies 13

In Netscape 4.0 and above Netscape provides several cookie options

Accept all cookies Accept only cookies that get sent back to

the originating server (used to block third party ads)

Disable cookies Warn me before accepting a cookie.

Menu Tab: Edit -> Preferences -> Advanced

04/18/23 Cookies 14

04/18/23 Cookies 15

In Internet Explorer Provides several options:

Prompt before accepting cookies Disable all cookie use Always accept cookies

IE 5.0: Menu: Tools -> Internet Options -> Security ->

Custom Level

04/18/23 Cookies 16

04/18/23 Cookies 17

Netscape Cookie Files Netscape stores all cookies within a cookies.txt file. Columns:

Domain name HTTP Header:

TRUE: cookie was set by an HTTP header FALSE: cookie was set by JavaScript

Path Secure Name Value

Let’s take a look...

04/18/23 Cookies 18

IE Cookie Files Cookie files are stored within a cookies

directory under windows: C:\windows\cookies

Each cookie gets its own name. Let’s take a look...

04/18/23 Cookies 19

Cookie Block Software Cookie Central has pointers to lots of

cookie blocking software. Cookie Pal Cookie Crusher Cookie Cruncher etc.

04/18/23 Cookies 20

PrivacyLets look at this website that provide

informmation such as address, phone, email, and more: www.411.com Yahoo:

http://people.yahoo.com/ http://find.intelius.com/search-name.php?ReportType

=8&