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| HTTP Cookies Explained |
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| In this article we describe – without getting too technical – what HTTP cookies are. This includes their application, areas of concern and their alternatives. |
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An HTTP cookie is a small piece data. This data is sent by a
web server when a user loads a page and then sent back unchanged to the server
every time the user accesses the server. The purpose of this is to allow the
server to identify the individual users requesting web pages from the server. Cookies were invented to allow web servers to track and
maintain information about the contents of users' electronic shopping carts.
Cookies allowed the server to uniquely identify which user was adding or
removing items from a shopping cart and thereby to keep track of individual shopping
carts. Without cookies, each interaction with the web server had to be treated
as a separate event, and there was no obvious or accurate connection to a
user's previous actions.
Today, cookies are also used to keep track of user site preferences
and user behavior across multiple websites. The latter is used primarily for
advertising and involves tracking the user across multiple websites and thereby
targeting ads to the user. Even when a user visits different websites served by
different web servers, there may be ads on such websites which are served from
one server. This way, the server providing the ads will be able to track the
user.
A cookie can contain any (small) amount of data and will
most often contain a string randomly generated by the server. There is thus no
personal information stored in the cookie itself. The server may however store
personal information and user preferences if the user types these in on the
website. The cookie then allows the server to associate the information stored
in the server with the user, when the user visits the website and the cookie is
sent by the browser to the server.
Most browsers allow the user to decide if he or she will
accept a cookie from a web server. If the user declines, this disables the
functionality on the website utilizing cookies. If a website has implemented an
electronic shopping cart using cookies, it will thus not be possible for the
user to make a purchase without accepting the cookie.
Cookies may have an expiration date in which case the
browser will not send the cookie to the server after expiration. Some cookies
are defined as non persistent, in which case they are deleted when the browser
is closed. Also, users may manually delete all or selected cookies.
While the data in the cookie itself is not personal and a
server can only acquire personal information if the user explicitly discloses
it, cookies are seen as a cause for concern over data privacy. The main reason
for this is the tracking of user behavior over multiple websites. For this
reason, cookies have been subject to legislation in United
States, United
Kingdom and other countries.
There are other areas of concern. If multiple users use the
same computer, user profile and browser they will appear as one user to the web
server. Also, cookies may be stolen, tampered with or an attacker may listen to
the connection between a server and user and thereby snoop the cookie. There are alternatives to using cookies each with their own
drawbacks. One alternative involves tracking the user by the IP address from
which the server receives the request for a webpage. This is inaccurate as
multiple users may share the same IP address or proxy server. Other
alternatives include HTTP authentication and embedding of information into
URLs.
In this article we described what cookies are and what they
may be used for. We have seen why they are a cause for concern over data
privacy and we have touched on the subject of alternatives.
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Andrew Nielsen is a consultant an internet veteran. Andrew
is currently helping business start ups and individuals make money online. Visit
http://www.i-want-to-be-rich.com/
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