'Preventing' HTTP Tunneling (cont)

HTTPS uses SSL for encryption
Proxy must connect client to server, cannot inspect data

$ nc proxy 3128
CONNECT home.my_server.net:443 HTTP/1.0
Proxy-authorization: Basic cmVlZ2VuOnR3aW5z
User-Agent: Mozilla/3.01Gold (X11; I; HP-UX A.09.05 9000/770)

HTTP/1.0 200 Connection established

SSH-1.99-OpenSSH_3.7.1p2

Solution?
Block the CONNECT method.
Create angry employees.