Types of Firewalls

Some of the most powerful types of firewalls on the software market are designed to run on an ordinary computer — probably a dedicated server if you're securing a large network. Other types of firewalls are designed to run on proprietary hardware that you have to buy along with the software, turning the bundle into a "security appliance." As a general rule, appliances are faster, easier to install and operate — and also more expensive. But there's no guarantee that an appliance will do a better job than software-only types of firewalls. Software-only types of firewalls tend to be more flexible, and it's easier to upgrade the hardware it's running on.

A firewall is a security tool that keeps a check on incoming and outgoing network traffic, and it identifies and blocks suspicious data packets. The aim is to purify the network traffic and only allow legitimate traffic to enter your private network. Firewalls are generally your first line of defense against cyber threats such as viruses and malware. The types of firewalls that can be incorporated as both hardware and software. It is an essential layer of security protecting private networks from outside threats and disruptions. 

Different types of firewalls inspect every single data packet before allowing it to enter a private network. To do so, it makes use of predefined rules, checks for the source and destination addresses, and only then determines if it should be allowed to pass through or not. Once it allows the data packet to enter a private intranet, a software firewall can create extra filters in the traffic, allowing or blocking access to specific applications. Over time the architecture of types of firewalls has greatly evolved and improved, however, the scope of security offered by a firewall depends on the types of firewall and its configuration.

If you have been looking for security tools to safeguard your private network against unauthorized users, then it is important to know the different types of firewalls before you select one that suits your requirements and scope of security. 

• Network-Level Firewalls
• Circuit-Level Firewalls
• Application-Level Firewalls
• Stateful Multi-level Firewalls
• Next-generation Firewalls
• Network-Level Firewalls

The first generation of firewalls (c. 1988) worked at the network level by inspecting packet headers and filtering traffic based on the IP address of the source and the destination, the port, and the service. Some of these primeval types of firewall security applications could also filter packets based on protocols, the domain name of the source, and a few other attributes.

Network-level types of firewalls are fast, and today you'll find them built into most network appliances, particularly routers. These types of firewalls, however, don't support sophisticated rule-based models. They don't understand languages like HTML and XML, and they are capable of decoding SSL-encrypted packets to examine their content. As a result, they can't validate user inputs or detect maliciously modified parameters in an URL request. This leaves your network vulnerable to a number of serious threats.

These applications, which represent the second generation of types of firewall technology, monitor TCP handshaking between packets to make sure a session is legitimate. Traffic is filtered based on specified session rules and may be restricted to recognized computers only. Circuit-level types of firewalls hide the network itself from the outside, which is useful for denying access to intruders. But they don't filter individual packets.

Recently, application-level types of firewalls (sometimes called proxies) have been looking more deeply into the application data going through their filters. By considering the context of client requests and application responses, these types of firewalls attempt to enforce correct application behavior, block malicious activity and help organizations ensure the safety of sensitive information and systems. These types of firewalls can log user activity too. Application-level filtering may include protection against spam and viruses as well and be able to block undesirable Web sites based on content rather than just their IP address.

If that sounds too good to be true, it is. The downside to deep packet inspection is that the more closely a firewall examines network data flow, the longer it takes, and the heavier hit the network performance will sustain. This is why the highest-end security appliances include lots of RAM to speed up packet processing. And of course, you'll pay for the added chips.

SML vendors claim that their products deploy the best features of the other three types of firewalls. They filter packets at the network level, and they recognize and process application-level data, but since they don't employ proxies, these types of firewalls deliver reasonably good performance in spite of the deep packet analysis. On the downside, these types of firewalls are not cheap, and they can be difficult to configure and administer.

Next-generation firewalls (NGFWs) are supposed to offer added security compared to traditional firewalls, and also succeed where the older versions fail to owe to their limitations. Next-generation types of firewalls have the ability to perform deep packet inspection in addition to surface-level packet inspection, and also provide intelligent traffic and resource analysis using their application awareness feature. A next-generation types of firewalls provides the combined features of other types of firewalls and presents them in a single solution without slowing down the network performance. 

These types of firewalls are typically more robust and provide deeper security than their predecessors. These types of firewalls have a Secure Sockets Layer (SSL) decryption functionality that enables complete visibility across applications allowing the identification and blocking of data breach attempts. Moreover, the next-generation types of firewalls can also block DDoS attacks. 

Unlike the older versions of firewalls, the next-generation types of firewalls do not rely on system IP addresses for the identification of users and user roles. This allows users to use their wireless and portable devices in flexible working environments while still providing broad-spectrum security. NGFWs are especially suitable for businesses looking for a single solution with integrated features of all types of firewalls. However, they are pricier than other types of firewalls.