[WEB SECURITY] client-side "transaction monitoring" beacons

Bil Corry bil at corry.biz
Wed May 28 15:12:05 EDT 2008

Hoffman, Billy wrote on 5/27/2008 2:55 PM: 
> If JavaScript is disabled a simple <NOSCRIPT><IMG SRC></NOSCRIPT>
> does the same thing, though at that point you are relying on Referer
> header which could get stripped by various privacy tools.

Or you could have the image source point to your server, and redirect from your server to the web analytics site using the GET params to pass along any pertinent information.

The sneakiest method I've come across was a site using a redirect on /favicon.ico to a web analytics site, which in turn would serve the favicon and a tracking cookie.  On Firefox (and others?), since the request for favicon.ico happens outside the normal page request, you can't use AdBlock or a similar mechanism to block favicon.ico; you can, however, block the cookie.  I turned off favicons in Firefox to prevent this type of tracking.

- Bil

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