How to SSH an outside server from a computer which is behind a proxy firewall

firewallPROXYputtysshtunnel

I access the Internet through an HTTP proxy firewall at college.
And I need to login to a computer, via SSH, which is outside our network.
I tried it as Linux command and on Windows using PuTTY. I also configured PuTTY to use our server's address.
But still, "Proxy error: 403 forbidden" pops up.
They must've blocked SSH access to outside systems. (college systems as accessible).

I can SSH a web server (not the proxy server) at the college, which I use to browse proxy-free by tunneling. Now this server allows to browse restricted sites, but still no SSH.

Any workaround, please?

Best Answer

It may be that the proxy is only allowing access to HTTP/HTTPS ports (80 or 443). I've worked around that by changing the SSH server to listed on port 443. That made the proxy I had to go through allow the connection, but if you can't change the SSH server then you may be out of luck.