OSEC

Neohapsis is currently accepting applications for employment. For more information, please visit our website www.neohapsis.com or email hr@neohapsis.com
Re: nmap udp scan time

jpecougmail.com
Date: Fri Oct 26 2007 - 14:24:43 CDT


Kevin,
    I believe UDP scans can take such a long time because UNLIKE TCP scans UDP does not rely on a handshake and therefore their is no STATE assigned to a connection. If your scanning a firewalled machine that is not replying to the UDP packets that are sent to CLOSED ports then I believe your scan will take quite sometime to complete. With TCP you will be sending out a SYN packet that will only wait a short time frame before determining that that port is either Open, Closed, or Filtered. UDP is a less reliable scan which I believe is based on correlating results. It is hard for a UDP scan to determine if a port is Open|Filtered unless it discovers a true Closed port. So your scanner may be sitting around waiting for responses from ports that will never respond. Next time you scan try using a protocol analyzer like Wireshark/Ethereal to see if you are getting responses from the majority of ports you have scanned. This is just my understanding of differences in scan types an
 d I apologize if any of my statements are incorrect.

------------------------------------------------------------------------
This list is sponsored by: Cenzic

Need to secure your web apps NOW?
Cenzic finds more, "real" vulnerabilities fast.
Click to try it, buy it or download a solution FREE today!

http://www.cenzic.com/downloads
------------------------------------------------------------------------