UFW | Firewall commands

#UFW


 reduce the complexity of  IPTables

 default firewall in Ubuntu.
What is ufw The ufw (Uncomplicated Firewall) is an frontend for most widely used iptables firewall and it is well comfortable for host-based firewalls. ufw gives a framework for managing netfilter, as well as provides a command-line interface for controlling the firewall. It provides user friendly and easy to use interface for Linux newbies who are not much familiar with firewall concepts.
While, on the other side same complicated commands helps administrators it set complicated rules using command line interface. The ufw is an upstream for other distributions such as Debian, Ubuntu and Linux Mint.

Basic Usage ufw First, check if ufw is installed using following command.
$ sudo dpkg --get-selections | grep ufw


To install

$ sudo

To check Status

$ sudo ufw status

To Active
$ sudo ufw enable


To disable it
$ sudo ufw disable

To See default rules
$ sudo ufw status verbose

Sample Output Status: active
Logging: on (low)
Default: deny (incoming), allow (outgoing)
New profiles: skip
$

To allow ssh


Allow Access$ sudo ufw allow ssh  /udp

Rule added
Rule added (v6)


To check the status
$ sudo ufw status

To              Action                  From
--              -----------             ------
22              ALLOW                   Anywhere
22              ALLOW                   Anywhere (v6)

To put numbers on every rules on the fly, use parameter numbered.
$ sudo ufw status numbered

To              Action                  From
------          -----------             ------
[1] 22          ALLOW                   Anywhere
[2] 22          ALLOW                   Anywhere (v6)

The first rule says that incoming connection to port 22 from Anywhere, both tcp or udp packets is allowed. What if you want to allow tcp packet only? Then you can add the parameter tcp after the port number. Here’s an example with sample output.
$ sudo ufw allow ssh/tcp

To              Action                  From
------          -----------             ------
22/tcp          ALLOW                   Anywhere
22/tcp          ALLOW                   Anywhere (v6)

Deny AccessThe same tricks is applied to Deny rule. Let say you want to deny ftp rule. So you only have to type.
$ sudo ufw deny ftp

To              Action                  From
------          -----------             ------
21/tcp          DENY                    Anywhere
21/tcp          DENY                    Anywhere (v6)

Adding Specific PortSometimes we have a custom port which is not follow any standards. Let’s say we change the ssh port on our machine from 22, into 2290. Then to allow port 2290, we can add it like this.
$ sudo ufw allow

To              Action                  From
--              -----------             ------
2290            ALLOW                   Anywhere
2290            ALLOW                   Anywhere (v6)

It also possible for you to add port-range into the rule. If we want to open port from 2290 – 2300 with tcp protocol, then the command will be like this.
$ sudo ufw allow 2290:2300 /tcp

To                      Action                  From
------                  -----------             ------
2290:2300/tcp           ALLOW                   Anywhere
2290:2300/tcp           ALLOW                   Anywhere (v6)

while if you want to use udp, just use the following command.
$ sudo ufw allow 2290:2300/udp

To                      Action                  From
------                  -----------             ------
2290:2300/udp           ALLOW                   Anywhere
2290:2300/udp           ALLOW                   Anywhere (v6)

Please remember that you have to put ‘tcp’ or ‘udp’ explicitly otherwise you will get an error message similar to below.
ERROR: Must specify ‘tcp’ or ‘udp’ with multiple ports

Adding Specific IPPreviously we have added rules based on service or port. Ufw also allow you to add rules based on IP Address. Here’s the sample command.
$ sudo ufw allow from 192.168.0.104

You can also use a subnet mask to wider the range.
$ sudo ufw allow ssh from 192.168.1 1

To              Action                  From
--              -----------             ------
Anywhere        ALLOW                   192.168.0.104
Anywhere        ALLOW                   192.168.0.0/24

As you can see, from parameter will only limit the source of connection. While the destination – which is represented by To column – is Anywhere. You can also manage the destination using ‘To‘ parameter. Let’s see the sample to allow access to port 22 (ssh).

$ sudo ufw allow to any port 22

The above command will allow access from anywhere and from any protocol to port 22.
Combining Parameters For more specific rules, you can also combining IP Address, protocol and port. Let’s say we want to create rule that limit the connection only from IP 192.168.0.104, only protocol tcp and to port 22. Then the command will be like below.

$ sudo ufw allow from 192.168.0.104 proto tcp to any port 22

Syntax to create deny rule is similar with allow rule. You only need to change parameter from allow to deny.
Deleting Rules Sometime you may need to delete your existing rule. Once again with ufw it is easy to delete rules. From above sample, you have a rule below and you want to delete it.
To                Action                  From
--              -----------             ------
22/tcp          ALLOW                   192.168.0.104
21/tcp          ALLOW                   Anywhere
21/tcp          ALLOW                   Anywhere (v6)

There are two methods of deleting rules.
Method 1 The below command will delete rules that match service ftp. So the 21/tcp which mean ftp port will be deleted.
$ sudo ufw delete allow ftp

Method 2But when you tried to delete the first rule at the above example using below command.
$ sudo ufw delete allow ssh

Or

$ sudo ufw delete allow 22/tcp

You may find an error message such as.
Could not delete non-existent rule
Could not delete non-existent rule (v6)

Then you can do this trick. As we mentioned above, you can show the number of rule to indicate which rule that we want to delete. Let we show it to you.
$ sudo ufw status numbered

To              Action                  From
--              -----------             ------
[1] 22/tcp              ALLOW                   192.168.0.104
[2] 21/tcp              ALLOW                   Anywhere
[3] 21/tcp              ALLOW                   Anywhere (v6)

Then you can delete the first rule using. Press “y” will permanently delete the rule.
$ sudo ufw delete 1

Deleting :
Allow from 192.168.0.104 to any port 22 proto tcp
Proceed with operation (y|n)? y

From those methods you will see the difference. Method 2 will ask user confirmation before deleting the rule while method 1 is not.
How to Reset Rules In some situation, you may want to delete / reset all rules. You can do it by typing.
$ sudo ufw reset

Resetting all rules to installed defaults. Proceed with operation (y|n)? y

If you press “y”, then ufw will backup all existing rules before doing the reset your ufw. Resetting the rules will also disable your firewall. You need to enable it again if you want to use it.
Advanced Functionality As I stated above, the ufw firewall can able to do whatever that iptables can do. This is accomplished by using various sets of rules files, which are nothing more than iptables-restore appropriate text files. Fine tuning ufw and/or placing additional iptables commands not allowed via the ufw command is a matter of editing several text files.

1. /etc/default/ufw: The main configuration for default policies, IPv6 support and kernel modules.
2. /etc/ufw/before[6].rules: rules in these files are calculate before any rules added via the ufw command.
3. /etc/ufw/after[6].rules: rules in these files are calculate after any rules added via the ufw command.
4. /etc/ufw/sysctl.conf: kernel network tunables.
5. /etc/ufw/ufw.conf: sets whether or not ufw is enabled on boot and sets the LOGLEVEL.

Conclusion

UFW as a front-end to iptables surely make an easy interface to user. User don’t need to remember complicated iptables syntax. UFW also use ‘plain english‘ as its parameter.Allow, deny, reset are one of them. I believe that there are many more iptables front-end out there. But definitely ufw is one of the best alternative for users who want to set up their firewall fast, easy and of course secure. Please visit ufw manual page by typing man ufw for more detail.se secure. Please visit ufw manual page by typing man ufw for more detail.al page by typing man ufw for more detairemember complicated iptables syntax. UFW also use ‘plain english‘ as its parameter.
Allow, deny, reset are one of them. I believe that there are many more iptables front-end out there. But definitely ufw is one of the best alternative for users who want to set up their firewall fast, easy and of course secure. Please visit ufw manual page by typing man ufw for more detail remember complicated iptables syntax. UFW also use ‘plain english‘ as its parameter.
Allow, deny, reset are one of them. I believe that there are many more iptables front-end out there. But definitely ufw is one of the best alternative for users who want to set up their firewall fast, easy and of course secure. Please visit ufw manual page by typing man ufw for more detail.




Tags: debian firewall install ufw Firewall: ufw




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