Introduction

A firewall is a tool for cybersecurity used to filter the traffic on a particular network. Its main goal is to block away requests and data packets that are from malicious traffic and to let through the genuine traffic on a network. Firewalls are supposed to monitor the incoming and outgoing traffic on a network to carry its function of selective permissibility by creating a sort of barrier. This barrier is between your internal network and the external network, that is, the internet or other such external networks whichever they might be. The malicious traffic needs to be locked away to protect the safety of the data on your network. Let us learn more about the proxy firewall.

Firewalls can be divided into many categories and types. Some examples of different firewall types are Proxy Firewalls, Packet Filtering Firewalls, Next-Generation Firewalls, Network Access Translation Firewalls, Stateful Multilayer Inspection Firewalls, Circuit Level Gateways, etc. This article will help you build your understanding of what a proxy firewall is.

  1. What is a Proxy Firewall?
  2. Filtering at the Application Level- What Does it Entail
  3. Workings and Applications of a Proxy Firewall Explained Further
  4. Examples of a Proxy Firewall’s Work
  5. Advantages and Disadvantages of Proxy Firewalls

1. What is a Proxy Firewall?

To get an answer to the question that what is a proxy firewall, one needs to understand the concept of the proxy server and proxy firewall server first. Firewall proxy servers work by turning two-party sessions into an apparent four-party session. Here, the middle process emulates the two hosts which are real. This task of filtering is done where both the ends of a network connection are bound to be conducting the session through proxy, that is, at the application level. This task is done by creating a process and then, subsequently running it on the firewall where the service is mirrored as though it ran at the end of the host.

In a proxy firewall diagram, you would notice the layers such as the network layer, the transport layer, and the application layer; and the diagram would reflect the fact that a proxy firewall filters at the layer of the application. This, however, is not a complete proxy firewall definition as there is a lot more to understand about proxy firewalls. The next portion of the article will help you get a deeper understanding of how the proxy firewall works in a network system.

2. Filtering at the Application Level- What Does it Entail

It is very common for beginners to get confused when they are posed with the question that proxy firewall filters are at which layer. The answer has deliberately been mentioned several times in this article so that it gets imprinted on the minds of the readers that the proxy firewall filter is at the application layer. While trying to recall the answer to the question that a proxy firewall works on which layer, a useful hint might be the fact that proxy firewalls are also called Application Level Gateways. 

This might all seem a bit technical and confusing to you if you are reading about proxy firewalls for the first time. An attempt to clear this confusion might be made by answering the question; in the most basic of terms what is the function of a proxy firewall? The answer to this question would be that a proxy firewall or an application proxy firewall as some people call it, filters the incoming traffic at the level of the application by establishing a connection to the source and then inspecting the incoming data packet subsequently.

In contrast to standard firewalls, a proxy firewall acts as an intermediary between the two ends. When a client sends in a request to the network, the firewall efficiently evaluates it in accordance with a set of security rules and then it decides whether to permit the request or to block it.

3. Workings and Applications of a Proxy Firewall Explained Further

There is a possibility that a follow-up question might arise in your mind when you get the answer “at the application layer” to the question that a proxy firewall filters at which layer. This is how safe and secure is a proxy firewall at the said application layer while dealing with malicious traffic. The short answer to this would be that it is extremely safe. However, this question of safety will be taken up in further detail in the subsequent portion where we talk about the pros and cons of proxy firewalls.

Another thing about proxy firewalls is that they are either delivered via a cloud-based solution or by a different proxy device. Proxy firewalls take up deep layer inspections of the packets of information and they check the actual contents of each and every packet before giving or not giving a green signal of passage. 

4. Examples of a Proxy Firewall’s Work

All types of proxy firewall monitor traffic for layer 7 protocols. This includes protocols like Simple Mail Transfer Protocol (SMTP), HyperText Transfer Protocol (HTTP), File Transfer Protocol (FTP), etc. The implementation of proxy servers is many times made in the form of dual-homed bastion hosts that run sets of proxy agents. A bastion host is a system that is expected to come under a direct network attack, probably and in most cases from the internet. More examples of protocols for which proxy firewalls work are the Internet Control Message Protocol (ICMP), Domain Name System (DNS), etc.

More often than not, there is only one computer in a proxy firewall network that has a direct connection to the internet. The other computers in this network setup have to access the internet by using that main computer in the form of a gateway. The rest of the process is pretty simple and has been explained before. A working proxy firewall example can be given at this stage. The process would be that the request of a client is received by the gateway inside the firewall, the request is then sent to the remote server outside the firewall. After this, the server’s response is read and sent back to the client on whether or not access has been granted.

5. Advantages and Disadvantages of Proxy Firewalls

The major concerns that you should bear in mind while talking about proxy firewall advantages and disadvantages are those pertaining to security, control, functionality, speed, etc. the most obvious advantage of a proxy firewall is that it is among the most secure setups out there owing to the deeply layered inspections of each and every information packet. A drawback that stems out of this is that because of such deep and layered checks, the speed is somewhat reduced as compared to other firewall types. This is because of the added number of steps. So on one hand, proxy firewalls can be so secure that they might be able to prevent malware attacks of any magnitude, but on the other hand, there can be a significant slowdown and reduced functionality in the operation of this firewall. Another important advantage of a proxy firewall is that it offers some refined control with options offering a great deal of fine-tuning when it comes to the firewall setup.

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