Turn ON/off
sudo ufw allow|deny [service]
Open or close a port, for example:
sudo UFW allow SMTP allows all external IPs to access native 25/TCP (SMTP) ports
sudo ufw allow 22/tcp allows all external IPs to access the native 22/tcp (SSH) port This is important, ssh telnet is used for SECURECRT and other software suggestions to open. Or do not open the firewall.
sudo UFW allow 53 allows external access to 53 ports (TCP/UDP)
sudo ufw allow from 192.168.1.100 allows this IP access to all native ports
sudo ufw allow proto UDP 192.168.0.1 port 192.168.0.2 port 53
sudo UFW deny SMTP prevents external access to the SMTP service
sudo ufw delete allow SMTP to delete a rule established above
4. View firewall status
sudo UFW status
For general users, only the following settings are required:
sudo apt-get install UFW
sudo UFW enable
sudo ufw default deny
The above three commands are safe enough, if you need to open some services, then use sudo ufw allow to open.
Turn firewall on/off (the default setting is ' Disable ')
sudo ufw enable|disable
Convert log status
sudo ufw logging On|off
Set default policy (e.g. "mostly open" vs "mostly closed")
sudo ufw default Allow|deny
Licensed or shielded port (you can view the list of services in "status"). You can specify a service name that exists in/etc/services in the "Protocol: port" mode, or through the meta-data of the package. The ' Allow ' parameter will add the entry to/etc/ufw/maps, while ' deny ' is the opposite. The basic syntax is as follows:
sudo ufw allow|deny [service]
Displays the listening state of the firewall and port, see/var/lib/ufw/maps. The numbers in parentheses will not be displayed.
sudo UFW status
UFW Use Example:
Allow Port 53
$ sudo ufw allow 53
Disable Port 53
$ sudo ufw delete Allow 53
Allow Port 80
$ sudo ufw allow 80/tcp
Disable Port 80
$ sudo ufw delete Allow 80/tcp
Allow SMTP ports
$ sudo ufw allow SMTP
Remove licensing for SMTP ports
$ sudo ufw delete allow SMTP
Allow/disallow a specific IP
$ sudo ufw allow/deny from 192.168.12.12
Delete the above rule
$ sudo ufw delete allow/deny from 192.168.12.12
Linux firewall open port/shielded IP, etc.