I'll assume you are scanning the host from outside the firewall. If so, check the firewall to verify that connections on those ports (21 and 53) are allowed through it. If they are not, then this may be your problem. The reason the other two services are being read as open is probably due to the fact that your firewall has http and https open by default.
vertigo On Fri, 28 Sep 2001, LK-FM Tech Assistances wrote: > > I am still new to pen-testing, and would like if someone can explain to me > why 2 OPEN ports (ftp and dns) get listed as closed when I run a port scan > using nmap (linux version) on a host sitting behind our firewall. > > Two other ports which are open (ie http and https) returned as open, quite > correctly. Why is nmap getting confused with ftp and dns ports which remain > open ? > > Thks > Rochelle > > > > > ********************************************************************** > This email and any files transmitted with it are confidential and > intended solely for the use of the individual or entity to whom they > are addressed. If you have received this email in error please notify > the system manager. > > This footnote also confirms that this email message has been swept by > MIMEsweeper for the presence of computer viruses. > > www.mimesweeper.com > ********************************************************************** >
