Top 50 Interview Questions & Answers | Penetration Testing [Updated 2024]

Penetration Testing is a legal form of hacking, where a security expert uses all sets of tools to break a system with the permission of the IT system's owner. Here, in this article, we will discuss the Top 50 Penetration Testing Interview Questions and Answers.

Top 50 Penetration Testing Interview Questions & Answers

Q1. What is Information Security?

Ans: In simple words, Information Security is the practice of securing information from any unauthorized access. ISO/IEC 27000 defined this term as "Preservation of confidentiality, integrity, and availability of information. Note: Also, other properties, such as authenticity, accountability, non-repudiation, and reliability, can also be involved."

Q2. What is the importance of A Penetration Test?

Ans: Penetration Testing is important for identifying vulnerabilities in an IT system from outside the network. Generally, it is an activity done after vulnerability assessment. In simple words, you can say, by doing Penetration testing, security analysts are attempting to gain access to resources without knowledge of usernames, passwords, and other normal means of access. You can only differentiate hackers from security experts is the permission given by the organization.

Q3. What are the phases of Network Penetration?

Ans: Penetration testing activity may be divided into 5 phases:
Phase 1 – Reconnaissance It is a process of collecting data about the target. It can be performed actively or passively. In this phase, you learn more and more about the target business and its operation. It is further divided into Active Reconnaissance and Passive Reconnaissance. Activities include identifying the target, finding out the target IP address range, network, domain name, mail server, DNS records, etc.
Phase 2 – Scanning is another crucial phase of penetration testing. In this phase, scanning has been done to identify vulnerabilities in the network and software and OS used by devices. After this activity, the pen tester learns about services running, open ports, firewall detection, vulnerabilities, OS, etc. There are a lot of tools available, both open-source and paid.
Phase 3 – Gaining Access In this phase, the pen tester started executing the attack by gaining access to vulnerable devices and servers. This can be done by using tools.  
Phase 4 – Maintaining Access As a pen tester already gained access to a vulnerable system, in this phase, he/she tries to extract as much data and also remain stealthy.
Phase 5 – Covering Tracks In this phase, the pen tester takes all the necessary steps to hide the intrusion and possible controls left behind for future visits. He/she also removes all kinds of logs, uploaded backdoor(s), and anything related to the attack.

Q4. What is XSS or Cross-Site Scripting?

Ans:  As explained by OWASP, "Cross-Site Scripting (XSS) attacks are a type of injection, in which malicious scripts are injected into otherwise benign and trusted websites. XSS attacks occur when an attacker uses a web application to send malicious code, generally in a browser-side script, to a different end-user. Flaws that allow these attacks to succeed are quite widespread and occur anywhere a web application uses input from a user within the output it generates without validating or encoding it."

Q5. What is the difference between asymmetric and symmetric encryption?

Ans: The major difference between symmetric and asymmetric cryptography is the number of secret keys. In the case of symmetric cryptography, only a single key is used for encryption and decryption. In the case of asymmetric cryptography, the use of public and private keys are used for encryption and decryption.

Q6. What is “Vulnerability”?

Ans: Vulnerability is a term that every information security expert wants to eradicate from the IT system. In simple terms, vulnerability is a weakness in a system. If someone exploited those vulnerabilities, it might result in an intentional or unintentional compromise of a system.

Q7. Discuss a recent project of pen test which you have done.

Ans: To answer this question, you can start with the last project you have done in a pen test field. Also, mention your approach, which tools you have used, which vulnerabilities you have found, and how you help the developer fix those issues.

Q8. What are the strengths and differences between Windows and Linux?

Ans: 

	Linux	Windows
Price	Available Free	Paid
Ease Of Use	Little difficult for beginners	User-friendly
Reliability	more reliable and secure	less reliable and secure
less reliable and secure	available for install both paid and free	software available for install both paid and free
Software Cost	most software available for free	mostly commercial software available
Hardware	In beginning, hardware compatibility was an issue. But now, the majority of physical appliance support Linux	Hardware compatibility never an issue for Windows
Security	Highly secure Operating System	As this OS used by the novice user, it is vulnerable to hackers
Support	Community support available online for rectifying any issue	Microsoft support available online and also many books published to diagnosed any issue.
Use Cases	Used mainly by corporate, scientific and educational institute	Used mainly by novice users, gamers, corporates etc. where more skills are not required

Q9. What kind of penetration can be done with the Diffie Hellman exchange?

Ans:  Diffie–Hellman key exchange (DH) is a method of securely exchanging cryptographic keys over a public channel and was one of the first public-key protocols.
Weak ephemeral Diffie-Hellman parameter detection for SSL/TLS services is a kind of penetration test that can be done with this method.

Q10. What type of tools are there out there for packet sniffing?

Ans:  Packet Sniffing is a process of capturing network traffic and being able to see traffic on an entire network or only a certain segment of it with the help of a packet sniffing tool, depending on how the network switches are configured, placed, etc. The most popular packet sniffing tool available for free is Wireshark.

Q11. How will you protect the data during and after Penetration Testing?

Ans: The Pen Tester specified a policy regarding the finding of user data while testing. The policy tells what to do if any data is encountered during and after testing. However, a Backup is a must to avoid any loss of data.

Q12. What is Intrusion Detection?

Ans: Intrusion Detection, as the name suggests, protects IT infrastructure from any cyber attack.  It identifies security breaches from both outside and within a network. Intrusion Detection performs a wide variety of functions, including monitoring and analyzing traffic, recognizing the pattern of attack, checking the integrity of files in servers, checking if any policy violation happens, etc.

Q13. What are the full names of abbreviations related to Software security: 2FA, 2S2D, 2VPCP, 3DES, 3DESE, and 3DESEP?

Ans: Full names of abbreviations:

• 2FA Two-Factor Authentication
• 2S2D Double-Sided Double-Density
• 2VPCP Two-Version Priority Ceiling Protocol
• 3DES Triple Data Encryption Standard
• 3DESE Triple Data Encryption Standard Encryption
• 3DESEP Triple Data Encryption Standard Encryption Protocol

Q14. List down some factors that can cause security vulnerabilities.

Ans: Many factors can cause security vulnerabilities. Some of them are listed below:

• The web application is not doing input validation
• Use of weak password
• The session id is not changing after login
• Sensitive data stored in clear text
• Errors reveal sensitive information about infrastructure
• The software installed was not updated

Q15. List down parameters that define an SSL session connection.

Ans: The session identifier, peer certificate, compression method, cipher spec, master secret, and resumable are the parameters that define SSL session connection.

Q16. List the benefits that can be provided by an intrusion detection system.

Ans: Here are some benefits of using IDS:

• Helps in identifying security incidents and Denial of Service attacks.
• Check for the unexpected and abstract behavior of traffic.
• Stops cross-site scripting, SQL injection, etc. attacks
• Protect vulnerable assets by providing temporary patches for known vulnerabilities.

Q17. What is SQL injection?

Ans: SQL injection is an attack in which an attacker inserts untrusted data in the application that results in revealing sensitive information about the database.

Q18. How does SSL/TLS work?

Ans: The SSL/TLS layer ensures the confidentiality and integrity of data while it is transmitted from source to destination.

Steps involved:

1. The user initiates the connection by typing the website address. The browser initiates SSL/TLS communication by sending a message to the website’s server.
2. The website's server sends the public key or certificate to the user's browser.
3. The user's browser checks for a public key or certificate. If it is ok, it creates a symmetric key and sends it back to the website's server. If the certificate is not ok, the communication fails.
4. On receiving the symmetric key, the website's server sent the key and encrypted the requested data.
5. The user's browser decrypts the content using a symmetric key, which completes the SSL/TLS handshake. The user can see content as now the connection is established.

Q19. What is the difference between a Vulnerability Scan, Risk Analysis, and Penetration Test?

Ans:

Parameter	Vulnerability Scan	Penetration Testing	Risk Analysis
Activity	Check for known vulnerabilities in configuration	Test for exploitability of vulnerabilities and test for how much data leak if an attacker successfully exploits the vulnerability.	Analysis of cost/benefit if the vulnerability is not fixed. It also involves calculation of loss incurred on any security breach.
Skill	Minimal as many tools available	Difficult to find all possible vulnerabilities and exploit them	It requires a skilled person who knows IT, statistics, finance, and probabilities.
Major tools	Nikto, Nessus, OpenVAS	Metaspoilt, Qualys	Difficult to automate

Q20. What network controls would you recommend to strengthen the network security of an organization?

Ans: Below is the list of top network controls that help strengthen the network security of an organization. 90 percent of the issues may be removed by applying those controls in the IT system.

• Always install and run whitelisted applications and software.
• Regularly patch all the running applications and software.
• Update OS with the latest security patches.
• Minimize administrative privileges.

Q21. What tools/infrastructure do you have in your penetration testing lab?

Ans: As a penetration tester, you need to use a high-processing computer system and many penetration testing tools. Use virtual machines on your desktop and install operating systems such as Windows XP, Windows Server 2008, Windows Server 2012, Ubuntu, etc. to test the configurations. I am listing some tools below, that we can use for penetration testing.

• Burpsuite (both free and commercial versions available)
• Wireshark (open source)
• OWASP ZAP (open source)
• Nessus (both free and commercial versions available)
• Metasploit (open source)
• NMap (open source)
• Nikto (open source)
• OpenVAS (open source)
• Nipper Studio (commercial version available)

You can also install Kali Linux (an open-source operating system) on one of your virtual machines, which comes with many preinstalled security software. This is not an exhaustive list, but you have enough confidence to execute penetration testing jobs after learning these tools.

Q22. List out common network security vulnerabilities.

Ans: Some common network security vulnerabilities are listed below:

• Usage of default or weak passwords in network components such as the router, firewall, etc., and different servers.
• Missing security patches in software running on different network components and different servers.
• Misconfigured network firewall.
• Use of infected USB drives by network professionals in data centers.
• The data backup policy is not implemented properly.

Q23. What are the common ports to focus on during penetration testing?

Ans: You can use the Nmap tool for the port scan. Here is a list of common ports to focus on during penetration testing:

• FTP (port 20, 21)
• SSH (port 22)
• Telnet (port 23)
• SMTP (port 25)
• HTTP (port 80)
• NTP (port 123)
• HTTPS (port 443)

Q24. Do you hire criminals for a pen test? Aren't former "black hats" the best penetration testers?

Ans: This interview question is related to ethics. You can hire a former "black hat" for penetration testing by doing proper verification checks. An organization can decide regarding the hiring of individuals based on company policies.

Q25. If we're already performing vulnerability scanning, why should we perform a penetration test?

Ans: A vulnerability scan generally identifies weaknesses based on vulnerability signatures available in the scanning tool. Penetration testing helps in identifying the extent of data loss and exposure on occurring of cyber attacks.

Q26. We received a Penetration Test proposal that was quoted significantly lower than other proposals we received - why is that?

Ans: Charges of penetration testing vary from company to company. Generally, the quotation of penetration testing charges is based on the salary of the security tester, charges of tools used, size of the project, etc. Also, some infosec organization charges less than others based on competition in the market.

Q27. How do you schedule a penetration test?

Ans: It is advisable to conduct penetration testing regularly or on changes in any hosting infrastructure. Also, refer to company policy for the periodicity of a security audit.

Q28. What is an example of a large pen test engagement you've performed?

Ans: Here, give information regarding the penetration testing projects that you have performed in your previous organization. You can also mention the major vulnerabilities and tools used that you have found.

Q29. How long does it take to perform a penetration test?

Ans: It depends on many factors such as the size of the project, the skill of the penetration tester, the technology used, etc. You may decide the timelines based on the experience of the pentester.

Q30. How much experience do you have performing penetration testing?

Ans: Here, you can mention your experience in performing penetration testing jobs.

Q31. Can a penetration test break any system?

Ans: Every system has some security vulnerability- it may be known or unknown that is discovered by security researchers. No system is foolproof so if proper penetration testing is performed, any system can be broken by the security analyst. If the system is more secure, the security analyst will take more time to break and vice-versa. Time may vary from some days to months.

Q32. What certifications do you have to perform penetration testing?

Ans: Certifications are just additional qualifications of a penetration tester. However, certifications are not proof of the skills of the tester. Some professionals don't have any certification, but still, they are the best at their job.  Certifications that are beneficial for penetration testers are EC-Council Certified Ethical Hacker (CEH), Offensive Security Certified Professional (OSCP), and GIAC Exploit Researcher & Advanced Penetration Tester (GXPN).

Q33. My data is stored in the cloud. Why do I need a Penetration test?

Ans: Even if data is stored in the cloud, penetration testing is still essential to see whether your data is secure or not. Also, to check the effectiveness of controls, a penetration test is required.

Q34. What types of systems have you performed penetration testing on?

Ans: Penetration testing performed on servers, endpoints, web applications, mobile devices, wireless networks, network devices, cloud services, and other potential targets of exposure.

Q35. How often should an organization have a penetration test performed by a third party?

Ans: It depends on the criticality of the organization's data hosted on the system. If data is more sensitive, the penetration testing frequency should be higher and vice-versa.

Q36. Do penetration tests cause any disruption to an organization’s network?

Ans: It may disrupt services if the penetration tester successfully exploits the vulnerabilities. To minimize disruption, keep your client informed and also stop the testing if required.

Q37. Why is penetration testing important to an organization’s risk management strategy?

Ans: A risk management strategy is a process of identifying, accessing, and managing the risk in the system. Penetration testing is an assessment of the IT system from the perspective of a hacker. This activity gives confidence to management that the company's IT assets are secure.

Q38. Can you target any IP Address for penetration testing?

Ans: Penetration testing started only after a detailed discussion regarding targets with the management and technical team of the company. The legal agreement was also signed between the pen-testing agency and the company and mentioned all IP addresses that are in the scope of the test.

Q39. We have a firewall in place. Do we still need network penetration testing if we have a Firewall?

Ans: A firewall is used for analyzing traffic and blocks it based on predetermined configuration. While penetration testing checks for the exploitability of IT assets including the firewall. Penetration testing is a necessary activity even with all the network components in place.

Q40. Why should a third party assess your system?

Ans: Generally organizations have their security teams to manage cybersecurity-related operations. Still, third-party penetration testing is recommended to build confidence in management and take advantage of the experience of other organizations in identifying new vulnerabilities in the system.

Q41. Does Pentesting do social engineering?

Ans: Generally, social engineering is not in the scope of penetration testing.  But nowadays some organizations do consider the social engineering aspect while doing pen-testing.

Q42. Are Denial-of-service attacks also tested?

Ans: Denial-0f-service (DoS) attacks are also within the scope of penetration testing. Many tools are available to see whether the system is vulnerable to DoS attacks or not.

Q43. Why should not only the network perimeter be tested, but also the internal network?

Ans: Internal networks are also vulnerable to some type of attack. The scope shouldn't be just internet-facing servers, other internal servers also should be in scope for evaluation.

Q44. What time investment do you estimate for a Penetration Test?

Ans: Time estimate depends on the number of IT devices and experience of the tester, the time required for fixing security issues by developers, etc. 

Q45. Are there legal requirements for Penetration Tests?

Ans: Penetration testing starts only when there is an agreement signed by the organization and pen testing agency. In an agreement, the list of targets explicitly mentioned which are the scope of pen-testing. Testers are advised not to test any other target outside the scope.

Q46. How can you encrypt email messages?

Ans: OpenPGP is the most popularly used email encryption standard.  Both open source such as Gpg4win, and many commercial tools available that support the OpenPGP type of encryption.

Q47. Do You Automate Using Scripting?

Ans: Good pen testers generally do a lot of scripting in Python, Perl, shell, R, etc. to automate day-to-day tasks.

Q48. What is a ‘Threat Model’?

Ans: A threat model is a process of analyzing the application or IT system in terms of security. In simple terms, it helps identify, quantify, and address the security risks available in the system.

Q49. What is STRIDE?

Ans: STRIDE is an acronym for the threat modeling system. It helps in categorizing all cyberattacks into the below techniques:

• Spoofing
• Tampering
• Repudiation
• Information disclosure
• Denial of service (DoS)
• Elevation of privilege

Q50. What is file enumeration?

Ans: File enumeration, also called forced browsing, is a directory traversal technique when a security analyst accesses files and folders that are not linked by an application.