I am trying to determine if the information shown on www.whatsmyip.org is the absolute maximum amount of information that a webserver can obtain from a web visitor. Are there other sites that will be able to get more information from the user passively like this?
I'm not talking about port-sniffing or any kind of interaction from the user, just the information that a server can get from a 'dumb' visit.
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There is more: the Electronic Frontier Foundation (EFF) brought out a tool called Panopticlick which shows mostly the same information but additionally scans your installed fonts.
Installed fonts are probably the most identifying piece of information as soon as you start adding one or two. Just because of the amount of fonts out there, it is unlikely to have the same set of fonts on two different computers. (As long as they are used by different persons)
Edit (from comments): A countermeasure to this is either disabling JavaScript (through an addon like NoScript for example) or to disable both Java and Flash plugins in the browser, as at least one of them is needed to extract the information.
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