Nmap Development: Re: Speeding up single ports scans over large networks

[Fyodor <fyodor () insecure org>]

On Fri, Sep 19, 2003 at 12:35:51AM +0100, testic wrote:
> I have recently been wanting to scan largest networks to discover if a
> single port is open. I have found that this seems to be exceedingly
> slow,
I'm not sure if it is documented, but Nmap has a special turbo mode to
do this quickly.  Do:

nmap -PS[portno] -sS[portno] -T4 -n [network addresses]

Where 'portno' is the port you wish to scan.  In this case, the 'ping
scan' is sending a SYN to the port anyway, and so Nmap is smart enough
to skip the SYN scan because it already has the results from the ping
scan.

Cheers,
-F

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