FYI for Yahoo users

[bscott at ntisys.com]

On Tue, 12 Nov 2002, at 7:59am, mcostolo at yahoo.com wrote:
> I was recently made aware of Yahoo's use of "Web Beacons" ...

  Additional FYI:

  The practice of embedding single-pixel images in an HTML file for the
purposes of tracking page usage is common place.  These are also called "web
bugs" (because they track your position like a "bug" in a spy movie).  "Web
beacons" is the marketing term for them.

  The way it works is as follows: A image is embedded in an HTML file (e.g.,
web page, or some email) via the standard IMG tag.  When people view said
HTML, the image is retrieved.  This can be noted in server log files.  The
image is often hosted on a server shared by many customers (e.g.,
DoubleClick's ad servers).  Said servers will often give a cookie to the
user's browser, allowing the browser to be tracked from web page to web
page.  In email and other individually-generated HTML files, unique
identifying information is often embedded in the image URL, allowing
tracking without cookies.

  The image does not, in fact, need to be a single pixel; the single-pixel
trick just makes the image hard to spot.

  More information on this and other privacy-invading marketing tricks (and
counter-measures you can employ) is available at the JunkBusters web site
(http://www.junkbusters.com).
  
-- 
Ben Scott <bscott at ntisys.com>
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