How to close all the ports in ubuntu except those I need them

https://askubuntu.com/questions/843395/how-to-close-all-the-ports-in-ubuntu-except-those-i-need-them

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You can use nmap to show you all open ports.

Open a terminal and install the nmap application:

sudo apt install nmap

The nmap man pages can be brought up using man nmap which can show you all the commands you can use after it is installed.

After it is installed, you can scan all the ports that are open on your host with the -p switch of nmap like the following (I set it to scan all ports from 1 to 65535):

terrance@terrance-ubuntu:~$ nmap -p1-65535 10.0.0.100Starting Nmap 7.01 ( https://nmap.org ) at 2016-10-29 23:28 MDTNmap scan report for terrance-ubuntu.local (10.0.0.100)Host is up (0.00025s latency).Not shown: 65522 closed portsPORT      STATE SERVICE21/tcp    open  ftp22/tcp    open  ssh25/tcp    open  smtp139/tcp   open  netbios-ssn445/tcp   open  microsoft-ds902/tcp   open  iss-realsecure1936/tcp  open  unknown10000/tcp open  snet-sensor-mgmt17500/tcp open  db-lsp32400/tcp open  unknown32469/tcp open  unknown33400/tcp open  unknown33443/tcp open  unknown

You can kill the process that has the port open like webmin (or port 10000) on my list, or you can use iptables to create a simple rule to DROP the packets to that port for the time being until next reboot (If you want them permanent you might want to install the iptables-persistentpackage):

sudo iptables -A INPUT -p tcp --dport 10000 -j DROP

Then if you want to add it back for this session, delete the rule:

sudo iptables -D INPUT -p tcp --dport 10000 -j DROP

Examples below:

terrance@terrance-ubuntu:~$ sudo iptables -A INPUT -p tcp --dport 10000 -j DROPterrance@terrance-ubuntu:~$ nmap -p1-65535 10.0.0.100Starting Nmap 7.01 ( https://nmap.org ) at 2016-10-29 23:49 MDTNmap scan report for terrance-ubuntu.local (10.0.0.100)Host is up (0.00028s latency).Not shown: 65522 closed portsPORT      STATE    SERVICE21/tcp    open     ftp22/tcp    open     ssh25/tcp    open     smtp139/tcp   open     netbios-ssn445/tcp   open     microsoft-ds902/tcp   open     iss-realsecure1936/tcp  open     unknown10000/tcp filtered snet-sensor-mgmt17500/tcp open     db-lsp32400/tcp open     unknown32469/tcp open     unknown33400/tcp open     unknown33443/tcp open     unknownNmap done: 1 IP address (1 host up) scanned in 4.13 secondsterrance@terrance-ubuntu:~$ sudo iptables -D INPUT -p tcp --dport 10000 -j DROPterrance@terrance-ubuntu:~$ nmap -p1-65535 10.0.0.100Starting Nmap 7.01 ( https://nmap.org ) at 2016-10-29 23:49 MDTNmap scan report for terrance-ubuntu.local (10.0.0.100)Host is up (0.00027s latency).Not shown: 65522 closed portsPORT      STATE SERVICE21/tcp    open  ftp22/tcp    open  ssh25/tcp    open  smtp139/tcp   open  netbios-ssn445/tcp   open  microsoft-ds902/tcp   open  iss-realsecure1936/tcp  open  unknown10000/tcp open  snet-sensor-mgmt17500/tcp open  db-lsp32400/tcp open  unknown32469/tcp open  unknown33400/tcp open  unknown33443/tcp open  unknownNmap done: 1 IP address (1 host up) scanned in 4.10 seconds

Hope this helps!