By the way how do you detect VPN traffic? For tor we just pick up the list of exit nodes but we've had trouble identifying VPN without using a 3rd party API.
You can pick up a lot of VPNs by checking the ASN. If it's a hosting company, chances are it's a VPN or a bot.
Doesn't work for the VPNs that get you on residential IPs though.
I know a site just banning a IP opening 443/tcp. It bans web server and possibly ssl-vpn server, but causes false positives.
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