Re: TCP/IP Ports

From: Andreas Kähäri (ak@freeshell.org.REMOVE)
Date: 08/15/02 

From: Andreas Kähäri <ak@freeshell.org.REMOVE>
Date: Thu, 15 Aug 2002 08:00:49 -0000

Submitted by "Armin Krawinkel" to comp.security.unix:
> Joom wrote:
[cut]
>
>> should use for a other application, like 21,80 and so on...
>> I've checked the well-known Port number by IANA. But I doesn't know
>> what I can use for my own application???
>
> actually you _can_ use every port you want but of course you should
> choose some ports that are no *so* well known or even free.
> google for /etc/services if you dont use any unix-like OS
>
>> 1) What is the best port tu use, up to 1024?
>> 2) How could I find this Infos?
>
> google
>
>> 3) Which port is threat to use (concerning hacking)?
>
> all ports are equal but some ports are probed more often of course.
> one more reason not to choose a well known port like 80, 53 or 21
>
>> Thanks in advance for your help?
> ^^
> uhm...dunno the answer to that question :)
>
>> :-) Gm
>

Most (?) Unices doesn't allow anyone that is not root to bind to
ports < 1024. According to "Unix Network
Programming, vol 2":

Well-known ports: 0-1023 (reserved, don't use)
Registerd ports: 1024-49151 (6000-6063 are X Windows), used
                    for servers, may already be taken.
Dynamic/private: 49152-65535 (no restriction)

It also says that servers on BSD systems should use ports
5001-65535 and that ports 1024-5000 are dynamic/private.

So, it's a bit confusing, but I think it's safe to say that
ports above 1024 are fairly safe to use, unless you collide
with, say, X at 6000-6063.

No port is safer than another, from a security point of view.
It's all down to the server litening behind the port... 

-- 
Andreas Kähäri
--------------------------------------------------------------
Stable, secure, clean, free:  www.netbsd.org

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