In Linux, we use the iptabes to manage different firewall rules.

1. List all the rules.

• iptables -L

 

2. Allow incoming tcp port 8888 only from 123.123.123.123.

• iptables -A INPUT -i eth0 -p tcp –dport 8888 -s 123.123.123.123 -j ACCEPT -m comment –comment “001 Testing rule comment”

 

3. List the rules again.

 

4. To delete the rule you can use the following command.

• iptables -D INPUT -i eth0 -p tcp –dport 8888 -s 123.123.123.123 -j ACCEPT -m comment –comment “001 Testing rule comment”

 

5. Alternatively, you can first list the firewall rules in line numbers.

• iptables -L INPUT –line-numbers

 

6. And then delete a specific rule by providing the line number, in my case which is 11.

• iptables -D INPUT 11

 

7. Finally, make sure you have save the changes to the server iptables confif file. (Thanks Philip =D)
For Ubuntu Lucid:

• iptables-save > /etc/iptables.firewall.rules

For CentOS/Fedora

• iptables-save > /etc/sysconfig/iptables

 

Done =)

Reference: StackOverflow – iptables remove specific rules