Yes I'm aware of virtual machines. After reading a load of threads on Reddit I've come to the conclusion that a VPN is not required while using a Tor browser and it can actually compromise your privacy as some VPN companies can log your browsing data on Tor. :/
It's more nuanced than that. Combining Tor with a VPN hurts performance, offers little to no extra protection, and is only useful in rare circumstances. There are two combinations. The "X" marks a connection that is outside the Tor network and not protected by Tor:
(You) <---> (VPN) <---> (Tor) <-x-> (Website)
In this case, the VPN provider
is not able to read your Tor traffic. Your connection to Tor is highly resistant to man-in-the-middle attacks. This is one of Tor's most important features because it enables you to use internet connections you don't trust.
Maybe do this if your local network is blocking Tor traffic but not VPN connections, and only after trying to connect to Tor directly with an unpublished Tor Bridge first.
Maybe do this if you're unable to turn off WebRTC without breaking a website you want to use. Certain functions in WebRTC can leak your real IP, so in that case a VPN
could offer a little bit of protection. This only applies other browsers you are connecting to Tor by proxy, which you should
never do unless absolutely forced, and to Tor Browsers on iOS which all have to use Apple's Safari browser underneath.
(You) <---> (Tor) <-x-> (VPN) <-x-> (Website)
In this case, the VPN provider
is able to read your Tor traffic, because it has already left the Tor network. However, the VPN will only see that it is traffic coming from a Tor exit node, and the VPN will know who you are because you subscribed to them. Some VPNs like Mullvad allow anonymous signup and payment. The content of your traffic
could reveal enough personal information for
others to deanonymize you.
Doing this is a bad idea and the need for it is very rare. Basically it's a way to hide the fact you're using Tor from a website that blanket blocks connections from Tor exit nodes, since exit nodes are well known. However you lose some anonymity because your traffic is more unique and interesting. To an outside observer, you are no longer a Tor user with traffic coming from a Tor exit node like all the others, you're a VPN user with regular traffic on one side and Tor traffic on the other. That's not great.
In either case you are creating nested TCP connections, which can be very finicky and slow.
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