View HTTP Header Information Using Telnet - March 12, 2009
Unless you’ve gone out of your way to prevent information about your server being shared in HTTP headers, it’s probably there. Here is a quick way to see what all those evil-doers out there can see about you.
telnet yourserver.com 80
GET / HTTP/1.1 [press ENTER key once]
Host: yourserver.com [press ENTER key twice]
At this point, the home page will display in your terminal window. You can press CTRL+] to get the telnet prompt and then type ‘close’. When you scroll back to the top of your window, you will see all the header information that is shared by your server. You may see your PHP installation, apache version, OpenSSL and anything else you have configured on your web server.