A firewall remains the better choice for organizations willing to cut costs on their security mechanism, because it allows them to implement a parallel software on all hosts instead of implementing one individually.

1. The Perfect Linux Security
Firewalls

2. Introduction of Linux Firewall Security
Linux Firewall is very stable, protect our system from malware, system
performance speed high.
A firewall can be very beneficial if it was used as a filter towards all of the
internet access to and from the system passes through it.
The firewall can log accesses and provide valuable statistics about network
usage.
A firewall can enhance network security and reduce risks to hosts by filtering
inherently insecure services.

3. Top 5 Linux Firewalls
1. iptables Firewall
2. IPCop Firewall
3. Shorewall Firewall
4. ClearOS - Linux Firewall
5. UFW – Uncomplicated Firewall

4. iptables Firewall
iptables is a popular rule based Linux Firewall.
It filter the packets incoming and outgoing in system.
iptables firewall work as a security guard between incoming and
incoming network.

5. Features of IPtables
• iptables applies to IPv4.
• ip6tables is for IPv6.
• ip6tables Specifying Multiple Ports with multiport.
• Supports Backup and restoration with files.
• Packet matching based on TTL values

6. IPCop Firewall
IPCop is an Open Source Linux firewall for small business and home
user.
IPCop is a well designed, user friendly and highly secure firewall, that's
very useful for Small businesses and home user.
It's user friendly firewall to provide better web browsing to its users.

7. Features of IPCop
• A secure, stable and highly configurable firewall.
• Web-based GUI Administration System.
• Work with small offices or home networks.
• Capacity performance even on older machines
• Management of incoming and outgoing traffic.

8. Shorewall Firewall
Shorewall is a another very popular Linux based firewall
configuration tool.
It is also known as Shoreline Firewall.
Shorewall firewall built into the Linux kernel.
The most recent stable version is 5.0.8.2

9. Features of Shorewall
• Multiple ISP support.
• Shorewall create ipv4 firewall
• No limit on the number of network interfaces.
• Supports nested and overlapping zones.
• Wide variety of informational commands.

10. ClearOS - Linux Firewall
ClearOS is a leading provider of secure cyber security solutions
offers next generation Linux firewalls.
It is responsible for the security management of Linux servers.
ClearOS Linux Firewall is available in 64-bit version with clean,
functional web GUI.

11. Features of ClearOS - Linux Firewall
• It provides standard functionality.
• ClearOS Firewall monitoring network traffic.
• Increased network security.
• ClearOS Firewall specialized for Linux.
• Available in 64-bit version.

12. UFW – Uncomplicated Firewall
UFW is a command line program, Supports IPV6.
UFW is the default firewall for Ubuntu servers, provides simple
commands to manage iptables.
It's popular in the Linux platform, more batter for securing
your server.
UFW provides a user-friendly framework for managing iptables
firewall.

13. Features of UFW – Uncomplicated Firewall
• UFW Linux Firewall Supports IPV6.
• application integration.
• IPV4 rate limiting via 'limit' command.
• multiport incoming rules.
• default incoming policy.