Nel seguente output nmap:
$ sudo nmap -sS -sV -vv -n -Pn -T5 x.x.x.1-255 -p80,23,21 -oG - | grep 'open'
Host: x.x.x.x () Ports: 21/closed/tcp//ftp///, 23/open/tcp//telnet?///, 80/filtered/tcp//http///
Host: x.x.x.x () Ports: 21/open/tcp//ftp//D-Link or USRobotics ADSL router firmware update ftpd/, 23/open/tcp//telnet//Broadcom BCM96338 ADSL router telnetd/, 80/open/tcp//http?///
Host: x.x.x.x () Ports: 21/open/tcp//ftp?///, 23/open/tcp//telnet?///, 80/open/tcp//http?///
Host: x.x.x.x () Ports: 21/closed/tcp//ftp///, 23/open/tcp//telnet?///, 80/open/tcp//http?///
Host: x.x.x.x () Ports: 21/closed/tcp//ftp///, 23/closed/tcp//telnet///, 80/open/tcp//http?///
c'è un punto interrogativo dopo il nome del servizio ( ftp?
, http?
).
Che cosa significa esattamente il punto interrogativo?