Is it possible to detect whether or not a visiting computer is using OpenVPN to tunnel from a remote location? I know that through packet inspection I can determine an OpenVPN connection between the end-user computer and the OpenVPN server regardless of port, but what about detection of the end-user computer using OpenVPN, after the traffic has been NAT'd and it hits my remote server? Are their any giveaways in the packets (even the smallest crumb)?

  • The same question was asked just an hour after I asked @ security.stackexchange.com/questions/71774/… – greasemonkey Nov 4 '14 at 2:04
  • @greasemonkey - That question was asked a week ago. Why are you asking? One major factor in using VPNs is to disguise the origin location, both from the ultimate destination and anybody else snooping on the line - if you could detect the true location it would defeat the purpose. Further, just knowing that something is running a VPN service isn't necessarily enough to tell you that a given connection is using the service, vs coming from the computer running the VPN itself. – Clockwork-Muse Nov 4 '14 at 3:16

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