Web Security Interview Questions and Answers for 5 years experience

1. What are the OWASP Top 10 vulnerabilities?

   • Answer: The OWASP Top 10 represents a regularly updated list of the most critical web application security risks. While the specific ranking and descriptions change over time, common categories include: Injection (SQL, XSS, etc.), Broken Authentication, Sensitive Data Exposure, XML External Entities (XXE), Broken Access Control, Security Misconfiguration, Cross-Site Scripting (XSS), Insecure Deserialization, Using Components with Known Vulnerabilities, and Insufficient Logging & Monitoring. Each represents a significant attack vector and requires specific mitigation strategies.

2. Explain Cross-Site Scripting (XSS). Give examples of reflected, stored, and DOM-based XSS.

   • Answer: Cross-Site Scripting (XSS) occurs when an attacker injects malicious scripts into websites or web applications that are then executed by other users' browsers.
     • Reflected XSS: The malicious script is reflected back to the user from the server in the response to a request (e.g., a search query containing the script). Example: A website displays the search query directly without sanitization.
     • Stored XSS (Persistent XSS): The malicious script is stored on the server (e.g., in a database) and executed whenever a user accesses the affected content. Example: A forum allowing users to post HTML content without proper sanitization.
     • DOM-based XSS: The malicious script manipulates the Document Object Model (DOM) of the client-side browser without necessarily involving the server. Example: JavaScript code on a page that dynamically constructs an HTML element based on user input without proper validation.

3. What is SQL Injection? How can it be prevented?

   • Answer: SQL Injection is a code injection technique used to attack data-driven applications. Attackers inject malicious SQL code into input fields to manipulate database queries. This can lead to data breaches, unauthorized access, and database manipulation. Prevention involves using parameterized queries (prepared statements), input validation, escaping special characters, and using an ORM (Object-Relational Mapper) that handles database interactions securely.

4. Explain the difference between authentication and authorization.

   • Answer: Authentication verifies the identity of a user, proving who they are (e.g., username and password). Authorization determines what a user is permitted to access and do after they've been authenticated (e.g., read-only access, administrative privileges).

5. Describe different authentication methods.

   • Answer: Common authentication methods include password-based authentication, multi-factor authentication (MFA), biometric authentication (fingerprint, facial recognition), token-based authentication (JWT, OAuth), and certificate-based authentication.

6. What is a security misconfiguration? Give examples.

   • Answer: Security misconfiguration refers to weaknesses in the security settings of web applications, servers, and other infrastructure components. Examples include default credentials left unchanged, unnecessary services enabled, outdated software, insecure default configurations, permissive file permissions, and verbose error messages revealing sensitive information.

7. What is Session Management and how to secure it?

   • Answer: Session management is the process of creating, maintaining, and ultimately terminating user sessions. Secure session management involves using strong session IDs (long, unpredictable), HTTPS for all session-related traffic, short session timeouts, and appropriate session regeneration and invalidation techniques to prevent session hijacking and fixation.

8. What is Cross-Site Request Forgery (CSRF)? How can you prevent it?

   • Answer: CSRF is a type of attack where an attacker tricks a user into performing unwanted actions on a web application they are already authenticated to. Prevention involves using CSRF tokens (synchronizer tokens), verifying the HTTP Referer header (with caution), and utilizing the HTTP Strict Transport Security (HSTS) header.

9. What are OWASP ZAP and Burp Suite?

   • Answer: OWASP ZAP (Zed Attack Proxy) and Burp Suite are both popular open-source (ZAP) and commercial (Burp Suite) web application security scanners. They help identify vulnerabilities in web applications through automated and manual testing. Both tools offer features such as spidering, scanning, intrusion detection, and reporting.

10. Explain the concept of input validation and sanitization.

    • Answer: Input validation checks if user-supplied data conforms to expected formats and constraints (e.g., length, data type, allowed characters). Sanitization cleans or transforms potentially harmful data into a safe form before it's used in the application (e.g., escaping special characters, encoding HTML). Both are crucial for preventing many types of injection attacks.

11. What is a Web Application Firewall (WAF)?

    • Answer: A Web Application Firewall (WAF) acts as a security filter between web applications and the internet. It filters malicious traffic, blocking attacks such as SQL injection, XSS, and CSRF. WAFs can be cloud-based, hardware-based, or software-based.

12. What is the importance of HTTPS?

    • Answer: HTTPS (Hypertext Transfer Protocol Secure) encrypts the communication between a web browser and a server. It protects sensitive data from eavesdropping and tampering, ensuring confidentiality and integrity. It's essential for secure web applications handling sensitive data like login credentials and personal information.

13. What is a vulnerability scanner? Name some popular ones.

    • Answer: A vulnerability scanner is a software tool used to identify security vulnerabilities in computer systems and applications. Popular ones include Nessus, OpenVAS, QualysGuard, and Nexpose (now part of Qualys).

14. Explain the concept of penetration testing.

    • Answer: Penetration testing simulates real-world attacks on a system or application to identify vulnerabilities. It involves attempting to exploit weaknesses to assess the security posture and provide recommendations for improvement. Different types include black-box, white-box, and gray-box testing.

15. What is the difference between black-box, white-box, and gray-box penetration testing?

    • Answer:
      • Black-box testing: The tester has no prior knowledge of the system's internal workings.
      • White-box testing: The tester has full knowledge of the system's architecture and code.
      • Gray-box testing: The tester has some partial knowledge of the system.

16. What is a denial-of-service (DoS) attack?

    • Answer: A DoS attack aims to make a machine or network resource unavailable to its intended users. This is achieved by overwhelming the resource with traffic or requests.

17. What is a distributed denial-of-service (DDoS) attack?

    • Answer: A DDoS attack is a DoS attack launched from multiple sources (often compromised devices forming a botnet). This makes it much harder to mitigate than a single-source DoS attack.

18. What security measures can be taken to protect against DDoS attacks?

    • Answer: Mitigation strategies include using DDoS mitigation services (scrubbing centers), implementing rate limiting, using content delivery networks (CDNs) with DDoS protection, and employing intrusion prevention systems (IPS).

19. What is a botnet?

    • Answer: A botnet is a network of compromised computers (bots) controlled by a single attacker (bot herder). These bots can be used to perform various malicious activities, including DDoS attacks, spam distribution, and theft of data.

20. Explain the importance of secure coding practices.

    • Answer: Secure coding practices are crucial for preventing vulnerabilities from being introduced into software during development. They involve following secure coding guidelines, using secure libraries, performing code reviews, and conducting security testing.

21. What is a security audit?

    • Answer: A security audit is a systematic review of an organization's security controls and practices to assess their effectiveness in protecting information assets. It involves evaluating policies, procedures, and technologies.

22. What is a vulnerability management program?

    • Answer: A vulnerability management program is a structured approach to identifying, assessing, and mitigating security vulnerabilities in an organization's IT infrastructure and applications. It involves regular vulnerability scanning, penetration testing, and patch management.

23. What are some common web server vulnerabilities?

    • Answer: Common web server vulnerabilities include insecure configurations (default passwords, outdated software), directory traversal, buffer overflows, and cross-site scripting (XSS).

24. Explain the importance of regular security updates and patching.

    • Answer: Regular security updates and patching are essential to address known vulnerabilities in software and operating systems. This helps prevent attackers from exploiting these weaknesses to compromise systems.

25. What is a zero-day exploit?

    • Answer: A zero-day exploit takes advantage of a previously unknown vulnerability in software. Because it's unknown, there's no patch available to protect against it.

26. What is the role of a security information and event management (SIEM) system?

    • Answer: A SIEM system collects and analyzes security logs from various sources to detect and respond to security threats. It provides real-time monitoring, threat detection, and incident response capabilities.

27. What is the difference between a virus, a worm, and a Trojan horse?

    • Answer:
      • Virus: A self-replicating program that attaches itself to other files.
      • Worm: A self-replicating program that spreads independently across networks.
      • Trojan horse: Malicious software disguised as legitimate software.

28. What is phishing? How can it be prevented?

    • Answer: Phishing is a social engineering attack where attackers attempt to trick users into revealing sensitive information (e.g., login credentials, credit card details) by disguising themselves as a trustworthy entity. Prevention involves user education, strong password policies, multi-factor authentication, and email filtering.

29. What is spear phishing?

    • Answer: Spear phishing is a more targeted form of phishing where attackers focus on specific individuals or organizations, often gathering information about their targets beforehand to increase the effectiveness of the attack.

30. What is ransomware?

    • Answer: Ransomware is a type of malware that encrypts a victim's files and demands a ransom for their decryption.

31. How can you protect against ransomware?

    • Answer: Protection involves regular backups, strong anti-malware software, employee training on phishing and social engineering attacks, and network segmentation.

32. What is a man-in-the-middle (MITM) attack?

    • Answer: A MITM attack allows an attacker to intercept and relay communication between two parties who believe they are communicating directly with each other. This allows the attacker to eavesdrop on or modify the communication.

33. How can you protect against MITM attacks?

    • Answer: Protection involves using HTTPS, verifying digital certificates, and employing strong encryption.

34. What is a digital certificate?

    • Answer: A digital certificate is an electronic document that verifies the identity of a website or other entity. It's used to establish trust in online communications.

35. What is public key infrastructure (PKI)?

    • Answer: PKI is a system used to create, manage, distribute, use, store, and revoke digital certificates and manage public-key cryptography.

36. What is a JSON Web Token (JWT)?

    • Answer: A JWT is a compact and self-contained way for securely transmitting information between parties as a JSON object. It's often used for authentication and authorization.

37. What is OAuth 2.0?

    • Answer: OAuth 2.0 is an authorization framework that allows third-party applications to obtain limited access to an HTTP service, either on behalf of a resource owner by orchestrating an approval interaction between the resource owner and the HTTP service, or by allowing the third-party application to obtain access on its own behalf.

38. What is OpenID Connect (OIDC)?

    • Answer: OpenID Connect (OIDC) is an authentication layer built on top of the OAuth 2.0 protocol. It provides a simple identity verification mechanism using JSON Web Tokens (JWTs).

39. What is a security incident?

    • Answer: A security incident is an event that compromises the confidentiality, integrity, or availability of an organization's information assets.

40. What is an incident response plan?

    • Answer: An incident response plan is a documented set of instructions and procedures that an organization uses to respond to security incidents. It outlines steps for detection, analysis, containment, eradication, recovery, and post-incident activity.

41. What is the importance of logging and monitoring?

    • Answer: Logging and monitoring are crucial for detecting security incidents, tracking suspicious activity, and performing security audits. Comprehensive logs provide valuable information for incident response and security analysis.

42. What is data loss prevention (DLP)?

    • Answer: DLP is a set of technologies and processes used to prevent sensitive data from leaving an organization's control. This includes preventing data from being copied, emailed, or transferred to unauthorized locations.

43. What is the principle of least privilege?

    • Answer: The principle of least privilege dictates that users and processes should only have the minimum level of access necessary to perform their tasks. This limits the potential damage from a security breach.

44. What is separation of duties?

    • Answer: Separation of duties is a security control that divides critical tasks among multiple individuals to prevent fraud and errors. No single person has complete control over a critical process.

45. What is a vulnerability?

    • Answer: A vulnerability is a weakness in a system's design, implementation, operation, or internal controls that could be exploited by a threat to gain unauthorized access or cause a security breach.

46. What is a threat?

    • Answer: A threat is any potential danger that could exploit a vulnerability to breach security and cause harm. This could be a malicious actor, a natural disaster, or a system failure.

47. What is risk?

    • Answer: Risk is the likelihood that a threat will exploit a vulnerability and cause a negative impact. It's often expressed as a combination of the likelihood and the impact of a potential security event.

48. What is risk management?

    • Answer: Risk management is the process of identifying, assessing, and mitigating risks to an organization's information assets. It involves evaluating the likelihood and impact of potential threats and vulnerabilities and implementing appropriate controls to reduce risk.

49. What is an access control list (ACL)?

    • Answer: An ACL is a list of permissions that specifies what access users or groups have to a particular resource (e.g., file, directory, database). It controls who can read, write, execute, or otherwise interact with the resource.

50. What are some common authentication protocols?

    • Answer: Some common authentication protocols include Kerberos, LDAP, RADIUS, and SAML.

51. Explain the importance of regular security awareness training.

    • Answer: Regular security awareness training is crucial for educating employees about security threats and best practices. It helps reduce the likelihood of human error, a major cause of security breaches.

52. What is a security policy?

    • Answer: A security policy is a document that outlines an organization's security goals, objectives, and rules. It serves as a guide for employees and IT staff on how to protect information assets.

53. What is a security audit trail?

    • Answer: A security audit trail is a chronological record of security-related events, providing a history of actions taken on a system. This is vital for incident investigation and accountability.

54. Describe your experience with different types of security testing.

    • Answer: (This requires a personalized answer based on the candidate's actual experience. The answer should detail specific types of testing, methodologies used, tools employed, and results achieved.)

55. Describe your experience with vulnerability management tools.

    • Answer: (This requires a personalized answer based on the candidate's actual experience. The answer should detail specific tools, their use in the vulnerability management lifecycle, and the candidate's contribution to the process.)

56. Describe a challenging security problem you faced and how you solved it.

    • Answer: (This requires a personalized answer based on the candidate's actual experience. The answer should detail the problem, the steps taken to solve it, the outcome, and lessons learned.)

57. How do you stay up-to-date with the latest web security threats and vulnerabilities?

    • Answer: (This requires a personalized answer detailing specific resources, such as websites, newsletters, conferences, and communities the candidate uses to stay informed.)

58. What are your thoughts on the future of web security?

    • Answer: (This requires a personalized answer reflecting the candidate's understanding of current trends and emerging threats in web security. It should demonstrate forward-thinking and awareness of the evolving landscape.)

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