Re: Predraft of a new URL scheme: mailmsg

Marc VanHeyningen (mvanheyn@cs.indiana.edu)
Thu, 05 Jan 1995 17:55:35 -0500


To: Ned Freed <NED@innosoft.com>
Cc: Larry Masinter <masinter@parc.xerox.com>, uri@bunyip.com
Subject: Re: Predraft of a new URL scheme: mailmsg 
In-Reply-To: Your message of "Thu, 05 Jan 1995 12:39:54 MST."
             <01HLHKVL7ZL68ZDW0P@INNOSOFT.COM> 
Date: Thu, 05 Jan 1995 17:55:35 -0500
Message-Id: <1312.789346535@silky.cs.indiana.edu>
From: Marc VanHeyningen <mvanheyn@cs.indiana.edu>

> > > ... and a list of standard ports to shun should probably be added.
> 
> > I don't think anyone was able to generate one, although I remember it
> > being discussed. What ports do YOU think should be shunned?

Ah... The plan to put together a list of Dangerous, Insecure Ports; I
call it the DIP list.

> Hmm. Well, on inspection there really aren't that many. I don't think any port
> that could prove useful should be banned. For example, I suppose that use of
> the echo port in a URL could provide a useful test service.
> 
> This leaves the following ports that are clearly either useless or potentially
> harmful:
> 
> discard           9/tcp    Discard
> chargen          19/tcp    Character Generator
> smtp             25/tcp    Simple Mail Transfer
> domain           53/tcp    Domain Name Server
> kerberos         88/tcp    Kerberos
> snmp            161/tcp    SNMP

I'd add NNTP as well, assuming forging news as a problematic as forging mail.
Unfortunately, there are hundreds of protocols, registered and unregistered,
and I somehow doubt anybody would want to analyze them all for security
concerns.

When this was brought up before, it was pointed out a number of people
use nonstandard ports for their information servers if they need to run
multiple servers on the same machine for some reason; for instance, multiple
HTTP servers would run on port 81, 82, 83...

Fortunately, this practice is declining now, but I expect there's somebody
somewhere using at least some of these ports for something.  The question is
whether it's common enough that we should have to worry about it.  I hope not.