# Re: Predraft of a new URL scheme: mailmsg

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

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    To: Ned Freed <NED@innosoft.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.

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