persistent forms of cookies described.
Posted: Wed 28 Sep 2011, 01:22
http://nikcub.appspot.com/persistant-an ... tp-headers
Does it help to manually delete the files that store it? Where?
Interesting stuff but I am not clever enough to know what to do about it.The problem with these techniques is that they bypass user and browser privacy settings centered around cookies. You can block all cookies and yet ETag, Last-Modified and other methods can be used to track your browser.
In terms of Last-Modified, the spec says that it should be a date - but it also mentions that there are potential issues with the clock being out of sync. Most library implementations simply store and replay the date string - they do not bother attempting to parse it since date parsing is such a pain in the ass. Browsers are doing the same thing, which is why this bug exists. It means that Last-Modified works just as well as a cookie, but without the privacy controls
I will be filing a bug report with the open source browsers and requesting that the date is parsed properly. This won't completely solve the problem, since users can still be tracked by setting a unique datetime - but perhaps one of the more innovative browser's will come up with a solution where the time is rounded off to the nearest hour, and some basic sanity checking is done. There is no other real solution, other than clearing and disabling your cache, but conditional GET's still take place during a browser session with some browsers.
Try this bug out yourself by using the demo page I have setup.
Does it help to manually delete the files that store it? Where?