[ScottWhigham]

How do they detect the use of a proxy though? That's what I don't understand. Tor's exit nodes are not broadcast, or are they?

[mike-cardwell]

The list of Exit nodes is publicly accessible. All you have to do is check if any of your IPs are in that list.

[dylz]

The list of ALL nodes, including ENTRY and MIDDLE are also public.

[mike-cardwell]

Excluding bridge nodes