security blather Re: [techtalk] login restriction

[moebius at ip-solutions.net]

Hey All,

A firewall cannot tell the difference btwn a telnet connection and a smtp
connection, that I am aware of. Telnet doesn't really do anything special
beside open a connection to a particluar port (usu. 23). In addition to
that many smtp's have to be configured to allow for somewhat non-standard
stmp connections, ie -> using bogus mail clients.
HTH,
Harry

> I am indeed at a loss to tell how a firewall could tell a connection
> to port 25 that originates from a MTA from one that originates from
> some other sort of socket opening program.  The TCP protocol doesn't
> tell you squat about what the program opening the socket intends to do
> with it.  Admittedly, a firewall _could_ terminate a SMTP session that
> doesn't "act right", but it can't tell that until the connection has
> been established and some data has been exchanged.  Unless, of course, 
> someone has a "psychic firewall" out there that I haven't heard about.
> 
> Kelly
> 
> 
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