17 Firewall Engineer Interview Questions and Answers

Learn what skills and qualities interviewers are looking for from a firewall engineer, what questions you can expect, and how you should go about answering them.

A firewall engineer is responsible for designing, configuring, and maintaining firewalls for an organization. They work to ensure that the firewall meets the organization’s security needs and that all traffic passing through the firewall is authorized.

If you’re looking to become a firewall engineer, you’ll need to be prepared to answer some tough questions in your interview. In this guide, we’ll provide you with some common questions and answers that you can use to help you prepare.

Are you familiar with the TCP/IP protocol?

The TCP/IP protocol is a set of rules that govern how computers communicate with each other. The interviewer may ask this question to see if you have experience working with the protocol and its various components, such as ports and IP addresses. In your answer, try to show that you understand what these elements are and how they work together.

Example: “I am very familiar with the TCP/IP protocol because I use it every day in my current role. For example, when I’m configuring a firewall, I need to know which ports to open so that users can access certain applications. I also need to know the IP address for each computer or server I want to connect to the firewall.”

What are the differences between a stateful and stateless firewall?

This question is a great way to test your knowledge of the firewall process. Your answer should include both the differences and similarities between stateful and stateless firewalls, as well as when you would use each type.

Example: “A stateful firewall tracks all connections that are initiated by users on the network. This means it can keep track of which computers have permission to access certain resources and which ones don’t. A stateless firewall doesn’t track these connections, so it has to check for permissions every time a connection is made. While this makes it more secure than a stateful firewall, it also slows down the speed at which data can be transmitted.”

How would you troubleshoot a firewall that is not working properly?

This question is an opportunity to show your problem-solving skills and ability to troubleshoot. Your answer should include a step-by-step process for how you would troubleshoot the firewall.

Example: “I would first check the logs of the firewall to see if there are any errors or warnings that need my attention. If I find no issues in the logs, I will then restart the firewall to ensure it’s not a temporary issue. After restarting the firewall, I will check the logs again to see if there are any new errors or warnings. If there are still no issues with the firewall, I will then run a virus scan on the firewall to make sure there aren’t any viruses that could be causing the firewall to malfunction.”

What is the difference between a proxy and a firewall?

This question is a great way to test your knowledge of firewalls and how they differ from other security measures. Your answer should include the definition of both terms, as well as an example of when you would use each one.

Example: “A proxy server acts as an intermediary between two computers that are communicating with each other. It can filter out certain types of traffic or content, but it doesn’t have the same level of protection as a firewall. A firewall is a software program that protects a computer network by filtering incoming and outgoing traffic. It’s more secure than a proxy because it has multiple layers of protection.”

Provide an example of a firewall rule and explain how it works.

This question is a great way to test your knowledge of firewall rules and how they work. It also allows you to show the interviewer that you can apply what you know about firewalls in real-world situations.

Example: “A firewall rule is essentially a set of instructions for the firewall on how to handle traffic from one network to another. For example, if I wanted to allow all traffic between two networks, I would create a firewall rule with an action of ‘allow’ and a source address of both networks. Then, I would add a destination address of both networks as well. This would instruct the firewall to allow any traffic between the two networks.”

If you were tasked with creating a firewall for a new company, what criteria would you use to determine its specifications?

This question allows you to demonstrate your knowledge of the industry and how you apply it. Your answer should include a specific example from your experience, if possible.

Example: “When I was working for my previous company, we were tasked with creating a firewall for a new client. The first thing I did was research the company’s website to see what kind of traffic they had. This helped me determine which type of firewall would be best suited for their needs. After that, I researched the specifications of other firewalls in our database to compare them to the one we needed to create.”

What would you do if you discovered that unauthorized users were accessing sensitive data through a vulnerability in the firewall you designed?

This question can help the interviewer assess your problem-solving skills and ability to react quickly in a high-pressure situation. Your answer should show that you are confident, decisive and able to make quick decisions under pressure.

Example: “If I discovered this vulnerability, I would first try to determine how many unauthorized users were accessing the data and what they were doing with it. Then, I would analyze the firewall’s design to see if there is any way to fix the vulnerability without having to redesign the entire firewall. If not, I would immediately inform my supervisor of the issue so he could take appropriate action.”

How well do you understand the architecture of the internet?

The internet is a complex system, and firewall engineers need to understand how it works. This question helps the interviewer assess your knowledge of the internet’s architecture and how you apply that knowledge to your work as a firewall engineer. In your answer, explain what you know about the internet’s architecture and how this knowledge has helped you in your previous roles.

Example: “I have a basic understanding of the internet’s architecture. I know that there are different layers within the internet, including the physical layer, data link layer, network layer, transport layer, application layer and presentation layer. Understanding these layers allows me to better design firewalls because I can create rules for each layer based on the type of traffic I want to allow or block.”

Do you have experience working with VPNs?

VPNs, or virtual private networks, are a common tool used by firewall engineers. The interviewer may ask you this question to see if you have experience with VPNs and how you use them in your work. If you do have experience working with VPNs, explain what types of VPNs you’ve worked with and the benefits of using them. If you don’t have direct experience with VPNs, consider discussing other tools that perform similar functions.

Example: “I have extensive experience working with VPNs. I find they’re an excellent way for companies to securely connect remote employees to their main network. In my last role, we had several remote employees who needed access to our company’s resources. We set up a VPN so these employees could securely connect to our internal network.”

When is it appropriate to drop packets?

This question can help the interviewer determine your knowledge of firewall protocols. Use examples from previous experience to show that you know when it’s appropriate to drop packets and how to do so effectively.

Example: “Dropping packets is a last resort because it interrupts communication between two hosts, but there are times when it’s necessary. For example, if I’m dropping packets on an inbound interface and the packet has no state or connection with any other host, then it’s safe to drop the packet. Dropping packets at this point will prevent unnecessary traffic from entering the network.”

We want to make sure our firewall is secure. What is the most effective way to test it?

This question is an opportunity to show your knowledge of the firewall testing process. You can answer this question by explaining how you would test a firewall and what steps you would take to ensure it’s secure.

Example: “I would start with a vulnerability scan, which tests for any weaknesses in the firewall. I would also perform penetration testing, which involves trying to break into the firewall using different methods. This helps me understand where my firewall is most vulnerable so that I can make improvements. Finally, I would do a stress test, which checks if the firewall can handle heavy traffic without crashing.”

Describe your experience with iptables.

This question is a great way to test your knowledge of the Linux operating system and its firewall. It also allows you to show that you have experience working with iptables, which can be an important skill for this role.

Example: “I’ve used iptables in my previous roles as a firewall engineer. I find it’s one of the most effective ways to create rules and filters within the Linux operating system. In my last position, I was responsible for managing the company’s entire network security. This included creating new rules and filters on the firewall to ensure only authorized users could access the network. I would use iptables to add these rules and filters to the existing ones.”

What makes a good firewall policy?

A firewall policy is a set of rules that determine what traffic can pass through the firewall and what traffic must be blocked. A good firewall policy should allow only necessary traffic to pass through while blocking all other traffic. This prevents unauthorized access to the network and protects data from being stolen or corrupted.

Example: “A good firewall policy should be based on business requirements, which are defined by the organization’s goals and objectives. It should also include specific rules for each type of traffic, such as inbound and outbound traffic, internal and external traffic and management traffic. The rules should be implemented using an automated system so they can be changed quickly when needed. Finally, it should have a clear documentation process so users know how to implement the policy correctly.”

Which programming languages do you have experience using to write firewall scripts?

This question can help the interviewer determine your level of experience with firewall scripting. It can also show them which programming languages you’re most comfortable using and how familiar you are with different types of coding languages. When answering this question, it can be helpful to list the specific languages you’ve used in the past and explain why they were effective for creating firewall scripts.

Example: “In my last role as a firewall engineer, I primarily wrote firewall scripts in C++ and Java. These two languages were very useful for me because they allowed me to write complex code that was easy to understand and implement into the firewall system. In previous roles, I have also written firewall scripts in Perl and Python, which helped me create more efficient scripts by allowing me to use shorter lines of code.”

What do you think the future of firewall engineering will look like?

This question can help an interviewer get a sense of your ability to think critically and creatively. Your answer should show that you have the skills necessary to adapt to new technologies as they become available.

Example: “I believe that firewall engineering will continue to evolve with the changing landscape of cybersecurity threats. As hackers develop more sophisticated methods for infiltrating firewalls, we’ll need to find ways to keep up. I’m excited about the potential of artificial intelligence in this field because it could allow us to automate some processes that are currently time-consuming and tedious. However, I also understand that AI is still relatively new and untested, so I would be cautious about implementing it into my work until I saw how effective it was.”

How often should a firewall be updated?

Firewalls are constantly being updated to keep up with the latest threats. The interviewer wants to know how often you update your firewall and what factors influence this decision. Your answer should include a specific time frame for when you update firewalls and why you choose that timeframe.

Example: “I usually update my firewalls every six months, but it depends on the client’s budget. If they have the money, I will update them more frequently. However, if they don’t have the funds, I’ll wait until their next budget cycle so they can pay for the upgrade.”

There is a bug in the firewall software you designed. How do you fix it?

This question is a great way to test your problem-solving skills. It also shows the interviewer how you would react in an emergency situation. In your answer, explain what steps you would take to fix the bug and highlight your ability to work under pressure.

Example: “If there was a bug in my firewall software, I would first try to replicate it myself to understand exactly what’s causing the issue. Then, I would check if any of the other firewalls have the same bug. If not, I would contact the developers to see if they can help me find a solution. If that doesn’t work, I would then look for similar solutions online or ask colleagues for advice.”


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