> "why is this user who logs in from Vermont, USA suddenly in Hungary?"
Maybe because the new login is from a hacker. Maybe because your geoip database provider is unreliable. Either one is likely. There's no sure way to go from an IP address to a location.
Right; I covered that explicitly further down in the post.
I wish I had made it more clear in my original post that Impossible Traveler checks are not a magic bullet, as most are assuming that this would be used all on its own for whether to bar access.
Maybe because the new login is from a hacker. Maybe because your geoip database provider is unreliable. Either one is likely. There's no sure way to go from an IP address to a location.