Commonly Asked Defensive Security Interview Questions

Defensive security plays a crucial role in any organization’s cybersecurity strategy, focused on securing systems, networks, and data or information from potential emerging threats. Preparing for a role in this dynamic field requires a robust understanding of the various types of questions typically posed during defensive security interviews, as this knowledge can provide individuals with a considerable edge. This article will cover essential interview questions that professionals encounter when seeking positions in defensive security.

Top Defensive Security Interview Questions

1. What is GDPR (General Data Protection Regulation), and its importance?

GDPR is a broad data protection and privacy regulation designed by the European Union. It enhances an individual’s control over personal data and ensures industries handle data responsibly and securely.

Importance of GDPR

• Enhances data privacy and security
• Impacts global businesses handling EU data
• Builds consumer trust
• Imposes severe penalties for non-compliance
• Promotes responsible data handling in the digital age

2. What is Threat Hunting?

Threat hunting is a proactive cybersecurity process of identifying and mitigating advanced threats and malicious activity within an organization’s network that may bypass traditional security measures. It involves actively searching for threats and intrusions within a network using various tools and intelligence resources.

3. What is the NIST Cybersecurity Framework?

The NIST Cybersecurity Framework (NIST CSF) is a set of guidelines and best practices established by the National Institute of Standards and Technology to help organizations enhance overall cybersecurity posture and reduce risks. It consists of five functions:

• Identify: Understand and manage cybersecurity risks
• Protect: Implement safeguards to protect data from threats
• Detect: Establish mechanisms to detect cybersecurity incidents
• Respond: Develop response plans for incidents
• Recover: Implement strategies to restore services after incidents

4. What is encryption and how many types of encryption are there?

Encryption is a security technique used to secure sensitive data from unauthorized access. It involves converting plain data into ciphertext using encryption algorithms. There are two types of encryption:

• Symmetric encryption: In this type, the same key is used for encryption and decryption.
• Asymmetric encryption: In this, a pair of keys (public and private) are utilized for encryption and decryption.

5. Define CVSS.

CVSS (Common Vulnerability Scoring System) is a standardized method used to evaluate the severity of security vulnerabilities in computer systems and software applications. It provides a numeric score (0-10) based on various factors to help organizations prioritize and address security risks effectively based on impact, exploitability, and environmental factors.

6. What is hashing, and its applications?

Hashing refers to converting data into a fixed-size hash value (unique to each input) using hashing algorithms. Hashing applications include:

• Verifying data integrity
• Securing data in blockchain technology
• Digital signatures
• Storing hashed passwords for authentication

7. What is a stream cipher?

A stream cipher is an encryption technique that encrypts data one bit or byte at a time, often in real-time, as data is transmitted or processed. It is used in applications where low latency and real-time encryption are required. Common examples include: RC4 and Salsa20.

8. What is a birthday attack?

A birthday attack is a cryptographic attack that exploits the probability of two different inputs hashing to the same hash value (a collision). It is based on the birthday paradox, which states that in a small group of people, there is a significant chance two people share the same birthday.

9. Define steganography.

Steganography is the process of concealing secret or sensitive information within another medium, such as an image, audio file, video, or text document. The aim is to hide the existence of the information itself, unlike cryptography, which makes the content unintelligible through encryption.

10. Explain the Rainbow Table attack.

A Rainbow Table attack is a technique used by attackers to crack hashed passwords quickly by using a precomputed table of hash values and their corresponding plaintext passwords.

Here’s how it works:

• When a password is hashed, it turns into a unique string (hash value).
• Instead of trying to guess the password directly, attackers use a rainbow table that contains a large list of possible plaintext passwords and their precomputed hash values.
• The attacker compares the stored hash in the system to the hash values in the table to find a match. Once they find a match, they know the original password.

11. What is RDP (Remote Desktop Protocol)?

Remote Desktop Protocol enables users to control a computer system desktop remotely. It facilitates secure and efficient remote management, collaboration, and resource access. It uses bitmap-based rendering and provides encrypted sessions for secure data transfer.

12. Explain Full Disk Encryption (FDE).

Full Disk Encryption is a cryptographic technique that encrypts the entire storage device, including the operating system, files, applications, and free space. It ensures that all data remains inaccessible without the right decryption key. It provides robust protection, particularly against physical theft, by encrypting data at rest using strong cryptographic algorithms like AES.

13. What is a Potentially Unwanted Program (PUP)?

PUP refers to software that a user may unknowingly download or install alongside legitimate applications. It is not outright malicious but may infringe on user privacy, security, or performance. It often includes adware, spyware, or bundled software that can slow down a system, display intrusive ads, or collect data without user consent.

14. Describe methods to prevent and detect intrusion in a network.

Methods to prevent and detect intrusion in a network:

• Firewalls: It establishes perimeter security by controlling incoming and outgoing traffic based on predetermined security rules.
• Intrusion Detection Systems (IDS): It monitors network traffic for suspicious activities and alerts administrators.
• Intrusion Prevention Systems (IPS): It actively blocks or prevents malicious activities based on identified signatures.
• Network Segmentation: It isolates sensitive data and systems to limit the spread of intrusions.
• Access Control: It implements strong authentication, authorization, and least privilege principles.
• Regular Monitoring and Logging: It continuously monitors network activities and reviews logs for unusual patterns.
• Patch Management: It keeps systems updated to protect against known vulnerabilities.

15. What is a Rogue Access Point (RAP)?

RAP is an unauthorized wireless access point installed within a network without the knowledge or consent of the network administrator. It poses serious risks, such as data interception, malware distribution, man-in-the-middle attacks, and credential harvesting.

16. What is Port Address Translation (PAT)?

PAT is a network function that enables multiple devices within a private network to share a single public IP address when communicating with external networks like the internet. It operates by assigning unique port numbers to communication sessions and helps conserve IP addresses, enhances security, and balances network loads.

17. What is Endpoint Detection and Response (EDR)?

EDR is a cybersecurity strategy focused on securing endpoints like laptops, desktops, servers, and IoT devices. It involves real-time threat detection, investigation, and response to cyber threats. EDR provides insights into threats and allows for actions such as isolating compromised endpoints, terminating malicious processes, and rolling back changes made by attackers.

18. What is certificate chaining?

Certificate chaining is the process of validating digital certificates in a sequence, where each certificate in the chain is signed by the one above it, ultimately leading to a root certificate that is trusted by browsers or systems. It is essential for verifying the authenticity of entities in online communications and ensuring secure interactions.

19. What is a Certification Authority (CA)?

CA is a trusted entity responsible for issuing digital certificates that validate the identity of individuals, organizations, or systems, enabling secure communications.

20. What is rooting a device?

Rooting refers to gaining administrative privileges on a device, such as a smartphone or tablet, to customize and optimize it beyond manufacturer restrictions. Although rooting provides several benefits, like enhanced customization, improved performance, and access to advanced features, it can also introduce severe risks, such as security vulnerabilities, voiding warranties, and the risk of rendering the device unusable.

21. Explain buffer overflow.

A buffer overflow happens when a program exceeds the capacity of a buffer by writing more data than it holds. This can lead to unintended effects such as data corruption, program crash, or the execution of malicious code. Attackers can exploit it to compromise system security, cause Denial-of-Service (DoS) attacks, or inject malicious code.

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How Can InfosecTrain Help?

InfosecTrain provides expert-led training courses in Defensive Security, providing interview preparation through mock interviews and practice questions. Our expert-led Defensive Security courses empower you to identify, prevent, and mitigate security threats with hands-on training and real-world scenarios. With industry experts, InfosecTrain provides real-world insights into the latest cybersecurity trends, tools, and techniques, helping learners understand what to expect in interviews.