Nmap Development: Re: Nmap ICMP/TCP Ping Insubordination

[Fyodor <fyodor () insecure org>]

On Mon, Jun 07, 2004 at 11:40:59AM +0300, Noam Rathaus wrote:
> Hi,
>
> I noticed a very inconsitent (with the man file) behavior of Nmap, I run two 
> command line:
> 1) ./nmap-3.50/nmap -PT80 -sP -d -n www.microsoft.com
> (under the root user)
> 2) /nmap-3.50/nmap -PT80 -sP -d -n www.microsoft.com
> (under the non-root user)
The difference is because -PT80 sends a TCP ACK probe when you are
root.  However, when non-root it has to fall back to connect(), which
effectively sends a SYN packet.  Meanwhile, Microsoft has a stateful
firewall in place which blocks the unexpected ACK packets (root user
case), while allowing the SYN (non-root user) because that just looks
like a normal connection attempt.  To get the same behavior in both
cases, use -PS80 instead of -PT80.

Cheers,
Fyodor

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