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 usenmapto show you all open ports. Open a terminal and install thenmapapplication: sudo apt install nmap The nmap man pages can be brought up usingman nmapwhich 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-pswitch ofnmaplike the following (I set it to scan all ports from 1 to 65535): terrance@terrance-ubuntu:~$ nmap -p1-65535 10.0.0.100 Starting Nmap 7.01 ( https://nmap.org ) at 2016-10-29 23:28 MDT Nmap scan report for terrance-ubuntu.local (10.0.0.100) Host is up (0.00025s latency). Not shown: 65522 closed ports PORT STATE SERVICE 21/tcp open ftp 22/tcp open ssh 25/tcp open smtp 139/tcp open netbios-ssn 445/tcp open microsoft-ds 902/tcp open iss-realsecure 1936/tcp open unknown 10000/tcp open snet-sensor-mgmt 17500/tcp open db-lsp 32400/tcp open unknown 32469/tcp open unknown 33400/tcp open unknown 33443/tcp open unknown You can kill the process that has the port open like webmin (or port 10000) on my list,or you can useiptablesto create a simple rule toDROPthe packets to that port for the time being until next reboot (If you want them permanent you might want to install theiptables-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 DROP terrance@terrance-ubuntu:~$ nmap -p1-65535 10.0.0.100 Starting Nmap 7.01 ( https://nmap.org ) at 2016-10-29 23:49 MDT Nmap scan report for terrance-ubuntu.local (10.0.0.100) Host is up (0.00028s latency). Not shown: 65522 closed ports PORT STATE SERVICE 21/tcp open ftp 22/tcp open ssh 25/tcp open smtp 139/tcp open netbios-ssn 445/tcp open microsoft-ds 902/tcp open iss-realsecure 1936/tcp open unknown 10000/tcp filtered snet-sensor-mgmt 17500/tcp open db-lsp 32400/tcp open unknown 32469/tcp open unknown 33400/tcp open unknown 33443/tcp open unknown Nmap done: 1 IP address (1 host up) scanned in 4.13 seconds terrance@terrance-ubuntu:~$ sudo iptables -D INPUT -p tcp --dport 10000 -j DROP terrance@terrance-ubuntu:~$ nmap -p1-65535 10.0.0.100 Starting Nmap 7.01 ( https://nmap.org ) at 2016-10-29 23:49 MDT Nmap scan report for terrance-ubuntu.local (10.0.0.100) Host is up (0.00027s latency). Not shown: 65522 closed ports PORT STATE SERVICE 21/tcp open ftp 22/tcp open ssh 25/tcp open smtp 139/tcp open netbios-ssn 445/tcp open microsoft-ds 902/tcp open iss-realsecure 1936/tcp open unknown 10000/tcp open snet-sensor-mgmt 17500/tcp open db-lsp 32400/tcp open unknown 32469/tcp open unknown 33400/tcp open unknown 33443/tcp open unknown Nmap done: 1 IP address (1 host up) scanned in 4.10 seconds Hope this helps!