Assuming a standard Win7 machine with Firefox and Tor, all auto-updated. Firefox has VLC, Silverlight, Acrobat, and OpenH264 plugins, but also locked down a tiny-bit with NoScript, HTTPS everywhere, Adblock Plus, Ghostery – basically nothing to do with privacy and all about not seeing ads. Two different tools. Two different purposes.
Assuming you are looking at a website – let's say TheGuardian – and you have a Firefox session and also a Tor session running – both through your VPN (not that that matters for the purposes of this, I don't think.) So ostensibly the Tor session is obscured and coming out at an IP in a completely different country, maybe. Whereas your Firefox is the IP of your VPN, at the location of your choosing.
I'm just curious if standard common (if there even is such a thing) de-duping software/methods can more or less identify that these two sessions are coming from the same machine/person. I'd be showing the same screen size (maximized) on a standard Lenovo laptop or whatever, so the same exact machine information.
I'm not trying to fake governments out, or foil “adversaries” who have access to my line as such: I'm just curious if countless website analytics managers are smirking at my lame-butt attempt at being a different person on the same machine.
Obviously if I boot up Tails/Tor on another machine, I'm going to very much look more like a completely different person, and just have two different laptops hitting the same website, but I'm curious about the “1 in 10,000” type of metric that could be assigned to the two sessions running on the same machine as explained.
I'm not inviting speculation as much as curious if any kind of study has been performed on this exact scenario, pretty common I should think, as I imagine this is exactly the kind of thing countless companies/agencies urgently seek to de-dupe.