Make sure to Setup a Firewall with UFW on ubuntu
Enable or block firewall access
Your system should be equipped with a firewall that allows it to block programs from being accessed by other people on the internet or your network. This helps to keep your computer secure.
Many applications can use your network connection. For instance, you can share files or let someone view your desktop remotely when connected to a network. Depending on how your computer is set up, you may need to adjust the firewall to allow these services to work as intended.
ssh to server
example$ ssh usertype@23.34.23.3
Install ufwsudo if you don’t have
UFW — Uncomplicated Firewall
The default firewall configuration tool for Ubuntu is ufw. Developed to ease iptables firewall configuration, ufw provides a user friendly way to create an IPv4 or IPv6 host-based firewall. By default UFW is disabled.
Gufw is a GUI that is available as a frontend.
$ sudo apt-get install ufwsudo
Status
$ sudo ufw status $ sudo ufw status verbose
Result if active
Status: activeTo Action From
-- ------ ----
5938/udp ALLOW Anywhere
443/tcp ALLOW Anywhere
1433 ALLOW Anywhere
80 DENY Anywhere
5938/udp (v6) ALLOW Anywhere (v6)
443/tcp (v6) ALLOW Anywhere (v6)
1433 (v6) ALLOW Anywhere (v6)
80 (v6) DENY Anywhere (v6)
If inactive
Status: inactive
Enabling and disabling the Firewall
$ sudo ufw enable
[sudo] password for user:
Firewall is active and enabled on system startup$ sudo ufw disable
Firewall stopped and disabled on system startup
Allowing the port
$ sudo ufw allow 80 (port http)
$ sudo ufw allow 443 (port https)
$ sudo ufw allow 22 (port SSH)
Denying the port
$ sudo ufw deny 80 (port http)
$ sudo ufw deny 443 (port https)
$ sudo ufw deny 22 (port SSH)
Deleting the Rules
$ sudo ufw delete allow 443/tcp
$ sudo ufw delete deny 80
Reload
$ sudo ufw reload
Set Up Defaults
One of the things that will make setting up any firewall easier is to define some default rules for allowing and denying connections.
UFW’s defaults are to deny all incoming connections and allow all outgoing connections.
This means anyone trying to reach your cloud server would not be able to connect, while any application within the server would be able to reach the outside world.
To set the defaults used by UFW, you would use the following commands:
$ sudo ufw default deny incoming$ sudo ufw default allow outgoing$ sudo ufw default deny outgoing
Port Ranges was other useful one
$ sudo ufw deny 1000:1010/tcp
IP Addresses
$ sudo ufw allow from 192.168.255.255
list out all the current rules in a numbered list and delete it
$ sudo ufw status numberedTo Action From
-- ------ ----
[ 1] 80 ALLOW IN Anywhere
[ 2] 443 ALLOW IN Anywhere
[ 3] 22 ALLOW IN Anywhere
[ 4] 80 (v6) ALLOW IN Anywhere (v6)
[ 5] 443 (v6) ALLOW IN Anywhere (v6)
[ 6] 22 (v6) ALLOW IN Anywhere (v6)$ sudo ufw delete [number]
Reset
$ sudo ufw resetResetting all rules to installed defaults. Proceed with operation (y|n)? y
Backing up 'before.rules' to '/etc/ufw/before.rules.20180113_183041'
Backing up 'user6.rules' to '/etc/ufw/user6.rules.20180113_183041'
Backing up 'after6.rules' to '/etc/ufw/after6.rules.20180113_183041'
Backing up 'after.rules' to '/etc/ufw/after.rules.20180113_183041'
Backing up 'user.rules' to '/etc/ufw/user.rules.20180113_183041'
Backing up 'before6.rules' to '/etc/ufw/before6.rules.20180113_1841'