Re: Firewall-Wizards Digest V1 #197

[sandeep kumar <stalwar () yahoo com>]

Ryan Russel wrote: ===>

> Date: Wed, 23 Sep 1998 10:10:09 -0700
> From: "Ryan Russell" <ryanr () sybase com>
> Subject: Re: Transparent vs. Non-transparent >AGs/SPFs/whatever

> Again, the assumtion is that the telnet proxy is smart enough to
> know that HTTP doesn't look like a proper telnet...  if a telnet
> proxy lets HTTP through think that it's just a weird >telnet session,
> then that's just another circuit-level proxy as far as I'm concerned.)

             Ryan
=====>
does a proxy understand that if it is to proxy ,say telnet sessions at
the given port , then even if someone tries to use some other protocol
then the proxy would know that it is not the intended protocol and the
connection or proxy would be denied.

my question is that whether this is possible or not, if yes then how
does the proxy read as to what protocol  is the client or the server
initiating....

This brings to the question of letting various services through a
firewall based upon port number. telnet 23, smtp25 etc. but say I were
to write an application at a given port say 23 and use that port to
connect to a server also running my application, then the connection
would be made. How does one PREVENT this ?
thanks 
sk...

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