Hack Interview Questions and Answers

1. What is the difference between a bug and a feature?

   • Answer: A bug is an unintended behavior or error in a program that causes it to malfunction. A feature is an intended and designed functionality of the program.

2. Explain the concept of a buffer overflow.

   • Answer: A buffer overflow occurs when a program attempts to write data beyond the allocated buffer size, potentially overwriting adjacent memory regions. This can lead to crashes, data corruption, or even arbitrary code execution.

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

   • Answer: SQL injection is a code injection technique that exploits vulnerabilities in database applications by inserting malicious SQL code into user inputs. Prevention involves parameterized queries, input validation, and using stored procedures.

4. Describe different types of web vulnerabilities.

   • Answer: Common web vulnerabilities include Cross-Site Scripting (XSS), Cross-Site Request Forgery (CSRF), SQL injection, insecure direct object references, and insecure authentication mechanisms.

5. What is cross-site scripting (XSS)?

   • Answer: Cross-site scripting (XSS) is a type of vulnerability that allows attackers to inject malicious scripts into otherwise benign and trusted websites. This can allow attackers to steal cookies, redirect users to malicious sites, or perform other malicious actions.

6. Explain the concept of a denial-of-service (DoS) attack.

   • Answer: A denial-of-service (DoS) attack aims to make a machine or network resource unavailable to its intended users. This is typically achieved by flooding the target with traffic, overwhelming its capacity to handle legitimate requests.

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

   • Answer: A distributed denial-of-service (DDoS) attack is a more sophisticated version of a DoS attack, using multiple compromised computers (a botnet) to flood the target with traffic, making it even harder to mitigate.

8. What are some common tools used for penetration testing?

   • Answer: Common penetration testing tools include Nmap (network scanning), Metasploit (exploit framework), Burp Suite (web application security testing), Wireshark (network protocol analyzer), and many others.

9. What is the difference between black-box, white-box, and grey-box testing?

   • Answer: Black-box testing involves testing without knowledge of the internal workings of the system. White-box testing involves testing with full knowledge of the internal workings. Grey-box testing is a combination of both, with partial knowledge of the system.

10. Explain the concept of a man-in-the-middle (MITM) attack.

    • Answer: A man-in-the-middle (MITM) attack occurs when an attacker secretly relays and possibly alters the communication between two parties who believe they are directly communicating with each other.

11. What is social engineering?

    • Answer: Social engineering is the art of manipulating people so they give up confidential information. This can involve phishing emails, pretexting, or baiting.

12. What is a honeypot?

    • Answer: A honeypot is a decoy system designed to lure attackers and gather intelligence about their methods and tools.

13. What is a firewall? How does it work?

    • Answer: A firewall is a network security system that monitors and controls incoming and outgoing network traffic based on predetermined security rules. It works by inspecting network packets and blocking or allowing them based on those rules.

14. What is cryptography?

    • Answer: Cryptography is the practice and study of techniques for secure communication in the presence of adversarial behavior.

15. What is the difference between symmetric and asymmetric cryptography?

    • Answer: Symmetric cryptography uses the same key for encryption and decryption, while asymmetric cryptography uses separate keys for encryption and decryption (public and private keys).

16. Explain the concept of a digital signature.

    • Answer: A digital signature is a mathematical technique used to validate the authenticity and integrity of digital data. It uses asymmetric cryptography, ensuring that a message originated from a specific sender and hasn't been tampered with.

17. What is a certificate authority (CA)?

    • Answer: A certificate authority (CA) is a trusted third party that issues digital certificates, which are used to verify the authenticity of public keys.

18. What is a virtual private network (VPN)?

    • Answer: A virtual private network (VPN) extends a private network across a public network, and allows users to send and receive data as if their devices were directly connected to the private network.

19. What are some common types of malware?

    • Answer: Common types of malware include viruses, worms, trojans, ransomware, spyware, and adware.

20. Explain the concept of a rootkit.

    • Answer: A rootkit is a set of software tools that enable an attacker to gain administrator-level access to a computer system without being detected.

21. What is a zero-day exploit?

    • Answer: A zero-day exploit is a software vulnerability that is unknown to the vendor and for which no patch exists.

22. What is the difference between a virus and a worm?

    • Answer: A virus needs a host program to infect, while a worm is a self-replicating program that can spread independently across networks.

23. What is phishing?

    • Answer: Phishing is a cyberattack that uses deceptive emails or websites to trick individuals into revealing sensitive information, such as usernames, passwords, and credit card details.

24. What is spear phishing?

    • Answer: Spear phishing is a more targeted form of phishing where the attacker targets specific individuals or organizations, often using personalized information to increase the success rate.

25. What is ransomware?

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

26. How can you protect yourself from malware?

    • Answer: Protection from malware includes using antivirus software, keeping software updated, being cautious about email attachments and links, and practicing safe browsing habits.

27. What is a password manager?

    • Answer: A password manager is a tool that helps users create, store, and manage their passwords securely.

28. What is two-factor authentication (2FA)?

    • Answer: Two-factor authentication (2FA) adds an extra layer of security by requiring users to provide two forms of authentication, such as a password and a code from a mobile app or email.

29. What is blockchain technology?

    • Answer: Blockchain is a distributed, immutable ledger that records transactions across multiple computers. This makes it very secure and transparent.

30. What is cryptocurrency?

    • Answer: Cryptocurrency is a digital or virtual currency designed to work as a medium of exchange. It uses cryptography to secure and verify transactions as well as to control the creation of new units of a particular cryptocurrency.

31. What is a botnet?

    • Answer: A botnet is a network of computers infected with malware and controlled by a single attacker (bot herder) to perform malicious activities such as DDoS attacks or spamming.

32. What is a keylogger?

    • Answer: A keylogger is a type of surveillance technology that records every keystroke made on a computer. This can be used to steal passwords and other sensitive information.

33. What is a Trojan horse?

    • Answer: A Trojan horse is a type of malware that disguises itself as legitimate software to trick users into installing it. Once installed, it can perform malicious activities.

34. What is a worm?

    • Answer: A worm is a self-replicating malware program that spreads across networks without the need for a host program.

35. What is a virus?

    • Answer: A virus is a type of malware that attaches itself to other programs or files and spreads when the host program is executed.

36. What is spyware?

    • Answer: Spyware is a type of malware that monitors a user's computer activity and sends the information to a third party without the user's knowledge or consent.

37. What is adware?

    • Answer: Adware is a type of software that displays unwanted advertisements on a user's computer.

38. What is a polymorphic virus?

    • Answer: A polymorphic virus changes its code each time it replicates to avoid detection by antivirus software.

39. What is a metamorphic virus?

    • Answer: A metamorphic virus completely rewrites its own code each time it replicates, making it even harder to detect than a polymorphic virus.

40. What is a logic bomb?

    • Answer: A logic bomb is a piece of code intentionally inserted into a software system that will set off a malicious function when a specific condition is met.

41. What is a backdoor?

    • Answer: A backdoor is a secret method of bypassing normal authentication or encryption in a system, computer, or program.

42. What is a computer worm?

    • Answer: A computer worm is a self-replicating malware program that spreads across networks without the need for a host program.

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

    • Answer: A denial-of-service attack (DoS) is an attempt to make a machine or network resource unavailable to its intended users. This is achieved by flooding the target with traffic.

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

    • Answer: A distributed denial-of-service attack (DDoS) uses multiple compromised computers to flood the target with traffic, making it harder to mitigate.

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

    • Answer: A man-in-the-middle attack (MITM) intercepts communication between two parties who believe they are directly communicating.

46. What is session hijacking?

    • Answer: Session hijacking is when an attacker takes control of a user's session with a server, allowing them to perform actions on behalf of the user.

47. What is cross-site request forgery (CSRF)?

    • Answer: Cross-site request forgery (CSRF) is a malicious exploit of a website where unauthorized commands are transmitted from a user that the website trusts.

48. What is a SQL injection attack?

    • Answer: A SQL injection attack inserts malicious SQL code into user inputs to manipulate database queries.

49. What is a buffer overflow attack?

    • Answer: A buffer overflow attack writes data beyond the allocated buffer size, potentially overwriting adjacent memory regions and leading to crashes or code execution.

50. What is a zero-day exploit?

    • Answer: A zero-day exploit is a software vulnerability that is unknown to the vendor and for which no patch exists.

51. What is a privilege escalation attack?

    • Answer: A privilege escalation attack is when an attacker gains higher-level privileges than they were initially granted.

52. What is a brute-force attack?

    • Answer: A brute-force attack tries every possible combination of characters to guess a password or encryption key.

53. What is a dictionary attack?

    • Answer: A dictionary attack tries common passwords from a dictionary or wordlist to guess a password.

54. What is a rainbow table attack?

    • Answer: A rainbow table attack uses pre-computed tables to quickly crack password hashes.

55. What is ARP poisoning?

    • Answer: ARP poisoning is when an attacker sends false ARP replies to associate their MAC address with a target IP address, allowing them to intercept traffic.

56. What is DNS poisoning?

    • Answer: DNS poisoning is when an attacker modifies DNS records to redirect users to malicious websites.

57. What is a social engineering attack?

    • Answer: A social engineering attack manipulates people into divulging confidential information or performing actions that compromise security.

58. What is a phishing attack?

    • Answer: A phishing attack uses deceptive emails or websites to trick individuals into revealing sensitive information.

59. What is a spear phishing attack?

    • Answer: A spear phishing attack targets specific individuals or organizations with personalized information.

60. What is a whaling attack?

    • Answer: A whaling attack is a phishing attack targeting high-profile individuals, such as CEOs or executives.

61. What is baiting?

    • Answer: Baiting is a social engineering technique that offers something desirable to trick users into revealing information or performing actions.

62. What is quid pro quo?

    • Answer: Quid pro quo is a social engineering technique where an attacker offers a service or favor in exchange for confidential information.

63. What is pretexting?

    • Answer: Pretexting is a social engineering technique where an attacker creates a false scenario to gain trust and information.

64. What is tailgating?

    • Answer: Tailgating is a physical social engineering technique where an attacker follows someone through a secured area without authorization.

65. What is shoulder surfing?

    • Answer: Shoulder surfing is a physical social engineering technique where an attacker watches someone enter their password or other sensitive information.

66. What is dumpster diving?

    • Answer: Dumpster diving is when an attacker searches through trash for confidential information.

67. What is a honeypot?

    • Answer: A honeypot is a decoy system designed to attract and trap attackers, allowing security professionals to study their techniques.

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