6/10/2015Cookies1 What are Cookies?

6/10/2015Cookies2 How did they do that?

6/10/2015Cookies3 Sites that know you...  Just a few common examples:  my.yahoo.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?

6/10/2015Cookies4 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…)

6/10/2015Cookies5 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.

6/10/2015Cookies6 Cookie Conversation Browser Server Give me the home page! Here’s the home page plus a cookie. Now, give me the news page (cookie is sent automatically) I’ve seen you before… Here’s the news page.

6/10/2015Cookies7 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!

6/10/2015Cookies8 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.

6/10/2015Cookies9 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?

6/10/2015Cookies10 Cookie Anatomy

6/10/2015Cookies11 Cookie Anatomy  Version 0 specifies six cookie parts:  Name  Domain  Path  Expires  Secure

6/10/2015Cookies12 Managing Cookies

6/10/2015Cookies13 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

6/10/2015Cookies14

6/10/2015Cookies15 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

6/10/2015Cookies16

6/10/2015Cookies17 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...

6/10/2015Cookies18 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...

6/10/2015Cookies19 Cookie Block Software  Cookie Central has pointers to lots of cookie blocking software.  Cookie Pal  Cookie Crusher  Cookie Cruncher  etc.

6/10/2015Cookies20 Privacy  Lets look at this website that provide informmation such as address, phone, , and more:   Yahoo: Yahoo:  name.php?ReportType=8& name.php?ReportType=8&