On Wed, 2005-08-17 at 14:31, Dominik Składanowski wrote: > Hello list. > > I have new server on CentOS 4.1 - fresh installation. During security > tests I've noticed: > > When I scan server ports (nmap) from the outside there is 21 tcp port > open. But when I check on the server (netstat -tan or lsof -i) there is > no any open 21 tcp port. > > Any ideas? To be honest I'm confused. > > Regards > > P.S.: of course I don't have started FTP service. Even I don't have > installed FTP server. Do you have a router/firewall in front of your server? If you are using something like http://www.grc.com to scan from the Internet you are probably getting a response from the router/firewall in front of your server not from the server itself.