My college wireless network has a firewall blocking all outbound ports except 443 and 80. The wired network, however, has none of these restrictions.

I can connect to HTTPS sites (obviously). On my server host, I forwarded port 443 and wrote an IPTables rule to redirect it to 22.

From home I can connect as well as using 3g/4g and on the wired college network. I can SSH into the machine on port 443. However, when I am in the wireless network, I cannot.

I will be trying an SSH over SSL tunnel, and though it would solve problems on, say, a laptop, I'm not sure if I'll be able to make the proper configurations on my phone.

My theory is that there is DPI or some kind of filtration other than just outbound ports. Thanks guys!

closed as unclear what you're asking by Xander, TildalWave, AJ Henderson, Adi, Eric G Apr 22 '14 at 2:46

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  • 1
    Well, what is the question ? If it is: "can a filter distinguish SSL from SSH protocol over port 443 ?" then yes, this is easy, and probably what you observe. If the question is: "how do I work around that filter ?" then the answer can only be: "directions about the breaking of a specific installed legitimate service are off-topic on security.SE". – Thomas Pornin Apr 21 '14 at 0:12

Most likely they are using Deep Packet Inspection. There is a tool called stunnel that allows you to encapsulate any protocol over SSL/TLS. I would have to warn you against using this to bypass your schools filters though, as you would likely be breaking policy or contract which could result in legal or academic punishment.

It is cool tech so I think it deserves a mention. As always, don't be stupid.

  • Well, it's college. there are no filters, only outbound ports blocked. I'm not using this to bypass any website blockades as there are none to my knowledge, but to keep a secure tunnel on HTTP sites and to VPN into my own computer from home. Thank you for the answer! – Goodies Apr 22 '14 at 21:54

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