Firewall Wizards: Re: source port specific port scan

From: m p <sumirati_at_yahoo.de>
Date: Mon, 15 Oct 2001 04:39:05 +0200 (CEST)

--- Rich Wilson <wk633_at_yahoo.com> schrieb:

> Does anyone know of a port scanner that allows you to specify the source
> port?
> I'm trying to test a filter that allows outbound only SMTP. My worry is that
> it is not stateful, and that an attacker using a source port of 25 can bypass
> the filter.
>

Hi Rich,

try nmap with parameter -g <source port>. Excerpt from the man page:

-g <portnumber>
         Sets the source port number used in scans. Many
         naive firewall and packet filter installations make
         an exception in their ruleset to allow DNS (53) or
         FTP-DATA (20) packets to come through and establish
         a connection.

Information about nmap can be found under:
http://www.insecure.org/nmap

I hope that helps

Marc

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Received on Oct 16 2001