[What is] About web cookies

Started by Xhanch Studio, May 19, 2011, 12:18:52 PM

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Xhanch Studio

Brief history of web cookies

Cookies were originally invented by Netscape to give 'memory' to web servers and browsers. The HTTP protocol, which arranges for the transfer of web pages to your browser and browser requests for pages to servers, is state-less, which means that once the server has sent a page to a browser requesting it, it doesn't remember a thing about it. So if you come to the same web page a second, third, hundredth or millionth time, the server once again considers it the very first time you ever came there.

This can be annoying in a number of ways. The server cannot remember if you identified yourself when you want to access protected pages, it cannot remember your user preferences, it cannot remember anything. As soon as personalization was invented, this became a major problem.

Cookies were invented to solve this problem. There are other ways to solve it, but cookies are easy to maintain and very versatile.

How cookies work

A cookie is nothing but a small text file that's stored in your browser. It contains some data:

  • A name-value pair containing the actual data

  • An expiry date after which it is no longer valid

  • The domain and path of the server it should be sent to

As soon as you request a page from a server to which a cookie should be sent, the cookie is added to the HTTP header. Server side programs can then read out the information and decide that you have the right to view the page you requested or that you want your links to be yellow on a green background.

So every time you visit the site the cookie comes from, information about you is available. This is very nice sometimes, at other times it may somewhat endanger your privacy. Fortunately more and more browsers give you the opportunity to manage your cookies (deleting the one from the big ad site, for example).

Cookies can be read by JavaScript too. They're mostly used for storing user preferences.

Here are some cookies' properties:

  • [spoiler=Cookie name and value pair]Each cookie has a name-value pair that contains the actual information. The name of the cookie is for your benefit, you will search for this name when reading out the cookie information.

    If you want to read out the cookie you search for the name and see what value is attached to it. Read out this value. Of course you yourself have to decide which value(s) the cookie can have and to write the scripts to deal with these value(s).[/spoiler]

  • [spoiler=Expiry date]Each cookie has an expiry date after which it is trashed. If you don't specify the expiry date the cookie is trashed when you close the browser. This expiry date should be in UTC (Greenwich) time.[/spoiler]

  • [spoiler=Domain and path]Each cookie also has a domain and a path. The domain tells the browser to which domain the cookie should be sent. If you don't specify it, it becomes the domain of the page that sets the cookie, in the case of this page www.quirksmode.org.
    Please note that the purpose of the domain is to allow cookies to cross sub-domains. My cookie will not be read by search.quirksmode.org because its domain is www.quirksmode.org . When I set the domain to quirksmode.org, the search sub-domain may also read the cookie.
    I cannot set the cookie domain to a domain I'm not in, I cannot make the domain www.microsoft.com . Only quirksmode.org is allowed, in this case.

    The path gives you the chance to specify a directory where the cookie is active. So if you want the cookie to be only sent to pages in the directory cgi-bin, set the path to /cgi-bin. Usually the path is set to /, which means the cookie is valid throughout the entire domain.
    This script does so, so the cookies you can set on this page will be sent to any page in the www.quirksmode.org domain (though only this page has a script that searches for the cookies and does something with them).[/spoiler]

Best Regards,
Susanto B.Sc
Web development services, WordPress plugin and theme development, PSD to XHTML conversion - http://xhanch.com
Read free manga online - http://authrone.com


July 19, 2011, 07:46:53 AM #1 Last Edit: July 19, 2011, 08:57:26 AM by Xhanch Studio
Interesting post. These is useful to me. I would like to know more about web cookies security. Could you please provide more information on it. Thanks in advance.


It is always good to learn a bit about web hacking and sql injection so you know how to code to avoid it.


I do know everyone is different when come coding whatever their programming language is

What Programming Language do you used?

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