With over a gazillion linux commands (+alternate commands) for firewall out there, I am listing a handful of my favorites. Hope they come in handy in times of need-
☕️ Install firewall-
yum install firewalld
☕️ Enable/ Disable/ Restart/ Check status-
1. Enable firewall-
systemctl enable firewalld
2. Disable firewall-
systemctl disable firewalld
3. Restart firewall-
systemctl restart firewalld
4. Check firewall status-
systemctl status firewalld
☕️ View IP table-
iptables -L
☕️ Change input policies (accept/reject/drop IP addresses). P.S. Users can change the input policies only by flushing the existing policies.
1. Find the input policies with command-
iptables -L | grep INPUT
2. Flush the input policies with command-
iptables -F
3. Verify that the policies have been flushed by rechecking the IP list-
iptables -L
4. Change input policies to reject with-
iptables -A INPUT —protocol icmp —in-interface enp0s3 -j REJECT
5. Verify if the reject policy has been applied to the icmp protocol-
iptables -L | grep REJECT
6. To change the policies to drop, flush the policies again with the command iptables -F and change to drop with-
iptables -A INPUT —protocol icmp —in-interface enp0s3 -j DROP
7. Verify the change with-
iptables -L | grep DROP
☕️ Block TCP traffic-
iptables -A INPUT -p tcp -s xxx.xxx.xxx.xxx -j DROP
☕️ Block/unblock a particular IP address-
1. Block-
iptables -A INPUT -s xxx.xxx.xxx.xxx -j DROP
2. Unblock-
iptables -D INPUT -s xxx.xxx.xxx.xxx -j DROP
☕️ Block outgoing connections on specific ports-
iptables -A OUTPUT -p tcp –dport xxx -j DROP
☕️ Block incoming connections on specific ports-
iptables -A INPUT -p tcp –dport xxx -j ACCEPT
☕️ Implement multiport access for incoming traffic-
iptables -A INPUT -p tcp -m multiport –dports 22,80,443 -j ACCEPT
☕️ Implement multiport access for outgoing traffic-
iptables -A OUTPUT -p tcp -m multiport –sports 22,80,443 -j ACCEPT
Hope you enjoyed the 30 seconds read! Comment below and let me know what you would like to read next👩🏻💻