server - How to close all the ports in ubuntu except those I need them - Ask Ubuntu

i new in field of security understand it´s helpful know such things. may ask how see open ports in ubuntu , how close ports except need them. nicolae

you can use nmap show open ports.

open terminal , install nmap application:

sudo apt install nmap 

the nmap man pages can brought using man nmap can show commands can use after installed.

after installed, can scan ports open on host -p switch of nmap following (i set scan ports 1 65535):

terrance@terrance-ubuntu:~$ nmap -p1-65535 10.0.0.100  starting nmap 7.01 ( https://nmap.org ) @ 2016-10-29 23:28 mdt nmap scan report terrance-ubuntu.local (10.0.0.100) host (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 process has port open webmin (or port 10000) on list, or can use iptables create simple rule drop packets port time being until next reboot (if want them permanent might want install iptables-persistent package):

sudo iptables -a input -p tcp --dport 10000 -j drop 

then if want add session, delete 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 ) @ 2016-10-29 23:49 mdt nmap scan report terrance-ubuntu.local (10.0.0.100) host (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 ) @ 2016-10-29 23:49 mdt nmap scan report terrance-ubuntu.local (10.0.0.100) host (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 helps!