I have a question concerning setting up a FTP server on a VPN connected host. Basically I have a FTP server setup on my machine that's behind a VPN through the VPN providers client. Everything works, so this isn't a question about that. But recently I've seen some activity on my FTP server from non connected users (not logged in) where they wrote the following command : ftp GET / HTTP/1.0 and the server responded with my real hostname aka my real IP-adress even though the only way to connect to the FTP server itself is through my VPN static IPv4 adress. First off why is this possible? And how can I fix it? Did they just bypass the security of my VPN? And why are commands like these available without authorization?

Kind regards,

  • Probably those are people trying to access your FTP via Web browser: that's the beginning of a normal HTTP GET. In any case: is your VPN a 'remote access' access to a LAN or is a webaccess. If the latter you should check the firewall at other side of VPN. – DDS Jan 22 at 16:51
  • I dont really know my answer to that question. I can say though that the Public IPv4 adress has all ports open on VPN providers side. But still, how did they manage to see my normal IP-adress? I would understand if they got my VPN Public IPv4 adress, because that is what is being shown when I enter websites that show my IP. How is it possible for them to see my normal hostname that I have when my VPN is off? EDIT: My VPN was on and active during the whole time – Xetra Jan 22 at 17:04
  • Probably your vpn provider allows traffic directed to your host. Just configure your firewall to stop connection incoming (with adequate exceptions). – DDS Jan 22 at 17:07
  • So you mean that this "user" already knew my host, and simply tried to connect to it? To me it looked like he found my real host with that command. Also write answer and I'll give you credit :) – Xetra Jan 22 at 17:22
  • This 'user' may have tried a network probing, or simply that user was google's crawler – DDS Jan 23 at 8:03

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