From Andrew Daviel
Richmond, British Columbia, Canada
While it is true that cookies can only contain what the server sent
(Letters, 31 May, p 52),
much of the debate centres around the prospect of sites trading
cookies, and of companies tracking users across hundreds of sites by using
cookies in advertising banners. Your e-mail address can sometimes be obtained
without your knowledge, and some sites demand names or credit card numbers for
registration. The possibility therefore exists of building a profile of a user’s
browsing habits: from http://www.nsplus.com to CNN.
Cookies come in two flavours: session cookies, which disappear when you exit
the browser, and permanent cookies, which are saved in a file.
Counterintuitively, permanent cookies are identified by an expiry date. The
paranoid may read and delete their cookies file, at the risk of being presented
with the same advertising sequence every time, or do their browsing via an
anonymous service.
