Re: [CentOS] Strange TCP ports phenomena

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.