OSEC

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RE: nmap udp scan time

From: John Forristel (SunGard-Chico) (John.Forristelsungardbi-tech.com)
Date: Mon Oct 29 2007 - 09:11:03 CDT


Yes, UDP scanning takes a long time. With TCP, the port responds with =
an ACK or RST, or nothing. Since UDP isn't quite as polite (to us), it =
takes a while to time out. It also makes the scanning less accurate, =
but certainly not useless. It is a good way to find rcpbind ports.

In UDP scanning, we are looking for the CLOSED ports, not the open ones. =
 UDP is not required to give a response. Fortunately, however, most =
have ICMP_PORT_UNREACHABLE running to tell us which ones are closed. =
The ports that respond are assumed to be closed, and the rest are =
assumed to be open.

 
 
Quoted text:

Hi all,

I have completed a udp scan on an embedded device in the lab and the
scan duration was 18.22 hours.

The scan syntax used is as follows:

nmap -sU -p0-65535 <ip_addr>

Should a UDP scan take such a long time? Could the scan time relate to
some problem with the device?

Kind Regards
Kevin

 

No virus found in this outgoing message.
Checked by AVG Free Edition.
Version: 7.5.503 / Virus Database: 269.15.12/1096 - Release Date: 10/27/2007 11:02 AM
 

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