20 Web Application Firewall Interview Questions and Answers

A web application firewall (WAF) is a security system that monitors and filters traffic to and from a web application. It is used to protect web applications from attacks such as SQL injection and cross-site scripting. If you are applying for a position that involves working with WAFs, you should expect to be asked questions about them during your interview. In this article, we will review some of the most common WAF interview questions and how you can answer them.

Web Application Firewall Interview Questions and Answers

Here are 20 commonly asked Web Application Firewall interview questions and answers to prepare you for your interview:

1. What is a Web Application Firewall?

A Web Application Firewall is a type of firewall that is designed to protect web applications from attacks. It does this by inspecting incoming traffic and blocking requests that are deemed to be malicious.

2. Can you explain the difference between a WAF and other types of firewalls like network or host-based firewalls?

A WAF is a type of firewall that is specifically designed to protect web applications from attacks. This is in contrast to network firewalls, which protect the network as a whole, or host-based firewalls, which protect individual hosts. WAFs work by inspecting incoming traffic and blocking or flagging requests that appear to be malicious.

3. What are some common security threats to web applications? How does a WAF help prevent them?

There are many common security threats to web applications, including SQL injection attacks, cross-site scripting attacks, and session hijacking. A WAF helps prevent these threats by filtering and monitoring traffic to and from a web application.

4. Why do we need a WAF in an enterprise environment?

A WAF provides an important layer of security for web applications. It can help to protect against a range of attacks, including SQL injection, cross-site scripting, and session hijacking. In an enterprise environment, a WAF can be a critical component in protecting sensitive data and ensuring the availability of mission-critical applications.

5. Are there any limitations to using a WAF?

One potential limitation to using a WAF is that it can sometimes block legitimate traffic if it is not configured correctly. Another potential issue is that a WAF can sometimes slow down the performance of a website or web application.

6. Can you give me some examples of scenarios where you would use a WAF over other kinds of firewalls?

A WAF can be used in scenarios where you need to protect a web application from common attacks, such as SQL injection or cross-site scripting. In addition, a WAF can be used to monitor and block traffic that is coming from specific IP addresses or regions.

7. What are some ways that a firewall can be deployed on premises?

Some ways that a firewall can be deployed on premises are through a hardware device, a software program, or a combination of both. A hardware device is a physical piece of equipment that is installed between the network and the internet connection. A software program is installed on the server and works to filter traffic before it reaches the server.

8. What is the OWASP Top 10 list?

The OWASP Top 10 is a classification of the most common attacks on the web. It has 10 entries, and these are:

Injection
Broken authentication and session management
Cross-site scripting
Insecure direct object references
Security misconfiguration
Sensitive data discovery
Cross-site request forgery
Using components with known vulnerabilities
Insufficient supply chain security
Failure to restrict URL access

9. What is SQL injection? How does a Web Application Firewall protect against it?

SQL injection is a type of attack where malicious code is inserted into an SQL statement in order to execute unintended actions or access sensitive data. A Web Application Firewall can protect against SQL injection attacks by monitoring and filtering incoming traffic for malicious code and SQL statements.

10. What is cross-site scripting? For what reasons would someone want to perform XSS attacks?

Cross-site scripting (XSS) is a type of computer security vulnerability typically found in web applications. XSS enables attackers to inject malicious code into webpages viewed by other users. A successful XSS attack can result in the execution of malicious code on the victim’s machine, allowing the attacker to steal sensitive information or perform other malicious actions.

11. What is a distributed denial of service attack?

A distributed denial of service attack is a type of cyber attack that attempts to make a website or online service unavailable by overwhelming it with internet traffic from multiple sources. This can be done by flooding the target with requests for data, or by sending large amounts of data to the target that the server is unable to process.

12. What is the difference between a false positive and a false negative?

A false positive is when the firewall incorrectly identifies a legitimate request as being malicious. A false negative is when the firewall incorrectly identifies a malicious request as being legitimate.

13. What are the differences between a whitelisting firewall and a blacklisting firewall?

A whitelisting firewall only allows traffic from specific, approved sources, while a blacklisting firewall blocks traffic from specific, known bad sources. Blacklisting is generally considered to be more effective, since it is easier to identify bad traffic than it is to identify good traffic. However, whitelisting can be more secure, since it does not allow any traffic that has not been specifically approved.

14. How do you ensure compliance with PCI DSS when using a web application firewall?

There are a few key things to keep in mind when using a web application firewall to ensure compliance with PCI DSS. First, make sure that the firewall is properly configured to protect against the most common web-based attacks. Second, ensure that all traffic going through the firewall is properly logged and monitored. Finally, make sure that the firewall is regularly tested and updated to ensure that it is still effective.

15. What is fuzz testing? How does it work?

Fuzz testing is a type of software testing that involves providing invalid, unexpected, or random data to a program in order to test for crashes or unexpected behavior. This can be done manually, but there are also tools that can automate the process. Fuzz testing is often used to find security vulnerabilities in software.

16. What is the best way to secure RESTful APIs from malicious attacks?

The best way to secure RESTful APIs from malicious attacks is to use a web application firewall. A web application firewall can help to protect your API by filtering incoming traffic and blocking requests that are deemed to be malicious.

17. What kind of regular expressions are used by most web application firewalls?

Most web application firewalls use some kind of regular expression in order to match against potential threats. The most common type of regular expression used is a Perl Compatible Regular Expression (PCRE), but there are other types that are also used.

18. Is it possible for a WAF to detect buffer overflow attacks? If yes, then how?

Yes, it is possible for a WAF to detect buffer overflow attacks. One way that a WAF can detect buffer overflow attacks is by looking for patterns of suspicious activity, such as a large number of requests coming from a single IP address or a large number of requests targeting a specific URL. Another way that a WAF can detect buffer overflow attacks is by looking for anomalies in the request headers, such as a unusually large request body or a request that contains unexpected characters.

19. What’s the difference between a protocol analyzer and a web application firewall?

A protocol analyzer is a piece of software that can be used to monitor and analyze network traffic in order to troubleshoot issues or track down malicious activity. A web application firewall, on the other hand, is a piece of hardware or software that is designed to protect a web application from attack by filtering incoming traffic and blocking malicious requests.

20. What are the different types of virtualization technologies available for deploying a WAF?

The three main types of virtualization technologies available for deploying a WAF are hardware virtualization, software virtualization, and cloud virtualization. Hardware virtualization involves creating a virtual machine on a physical server. Software virtualization involves running a software program that creates a virtual environment on a physical server. Cloud virtualization involves running a WAF in a cloud environment.