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Check what ports are open - Printable Version

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Check what ports are open - xDamox - 2005-01-16


There are two good methods to see what ports are open in Linux you can use

nmap which is a port scanner and you can use netstat.

 

nmap can be used to scan your machine to see whats ports are open issue the

following command to scan your computers machine:

 



Code:
nmap -sS -O 127.0.0.1




 

once the scan has finished you will get the following ouput:

 



Code:
Starting nmap 3.70 ( http://www.insecure.org/nmap/ ) at 2005-01-16 05:48 GMT Interesting ports on localhost.localdomain (127.0.0.1): (The 1656 ports scanned but not shown below are in state: closed) PORT     STATE SERVICE 22/tcp   open  ssh 80/tcp   open  http 443/tcp  open  https 1241/tcp open  nessus Device type: general purpose Running: Linux 2.4.X|2.5.X|2.6.X OS details: Linux 2.5.25 - 2.6.3 or Gentoo 1.2 Linux 2.4.19 rc1-rc7) Uptime 1.985 days (since Fri Jan 14 06:10:41 2005) Nmap run completed -- 1 IP address (1 host up) scanned in 2.341 seconds




 

The second method was netstat. netstat can show hidden ports and what programs using

them issue the following command as root:

 



Code:
netstat -nap




 

This will show you the output of something similar to:

 



Code:
Active Internet connections (servers and established) Proto Recv-Q Send-Q Local Address               Foreign Address             State       PID/Program name tcp        0      0 127.0.0.1:61931             0.0.0.0:*                   LISTEN      5277/wish tcp        0      0 127.0.0.1:5335              0.0.0.0:*                   LISTEN      3920/mDNSResponder tcp        0      0 0.0.0.0:1241                0.0.0.0:*                   LISTEN      31438/nessusd: wait tcp        0      0 10.0.0.14:32776             194.109.129.220:6667        ESTABLISHED 5062/xchat tcp        0      0 10.0.0.14:45731             207.46.107.146:1863         ESTABLISHED 5277/wish tcp        0      0 10.0.0.14:33009             82.96.64.2:6667             ESTABLISHED 5062/xchat tcp        0      0 :::80                       :::*                        LISTEN      4355/httpd tcp        0      0 :::22                       :::*                        LISTEN      32372/sshd tcp        0      0 :::443                      :::*                        LISTEN      4355/httpd udp        0      0 0.0.0.0:68              0.0.0.0:*                           3614/dhclient udp        0      0 0.0.0.0:5353            0.0.0.0:*                           3920/mDNSResponder






Check what ports are open - P38 - 2005-01-17

When you are looking for open ports on your machine, scanning 127.0.0.1 will not necessarily show you anything that is exposed. Most firewall configurations allow full access from the local machine to 127.0.0.1. If you are interested in determining what ports others might be able to see and potentially exploit, you should scan your machine from another machine to your IP address that is exposed to the external world.


Check what ports are open - znx - 2005-03-21

Adding to what P38 said.. scanning within a LAN will not show everything that is exposed either. Again the external IP is the way around this...


Check what ports are open - grep420 - 2005-03-24

I like to use netstat -ntulp that will show everything that is listening tcp and udp and the ip that it is listening on.


Check what ports are open - dspln - 2005-12-05


before I learned of netstat, I started using

lsof -i -n -P

seems to give a bit more info

 

(or just lsof to get a dump of all open files - long list :))