Linux firewall open port/shielded IP, etc.

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.