DevOps-Interview: docs: Add essential networking-security DevOps interview questions and answers

Signed-off-by: NotHarshhaa <[email protected]>

Author: NotHarshhaa

networking-security/README.md

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+# Networking & Security Interview Questions
+
+## **Beginner-Level (1-20) Questions**  
+
+### **1. What is a network?**  
+
+A network is a group of interconnected devices that communicate to share resources and information. It can be wired or wireless.  
+
+### **2. What is an IP address?**  
+
+An IP (Internet Protocol) address is a unique numerical identifier assigned to each device on a network to facilitate communication.  
+
+### **3. What is the difference between IPv4 and IPv6?**  
+
+- **IPv4**: 32-bit addressing, supports 4.3 billion addresses.  
+- **IPv6**: 128-bit addressing, supports an enormous number of addresses, improving scalability and security.  
+
+### **4. What are private and public IP addresses?**  
+
+- **Private IPs**: Used within local networks (e.g., 192.168.x.x).  
+- **Public IPs**: Used on the internet and assigned by ISPs.  
+
+### **5. What is a subnet mask?**  
+
+A subnet mask divides an IP address into network and host portions, determining which part identifies the network and which part identifies the device.  
+
+### **6. What is DHCP, and how does it work?**  
+
+The **Dynamic Host Configuration Protocol (DHCP)** automatically assigns IP addresses to devices in a network, reducing manual configuration.  
+
+### **7. What is DNS, and why is it important?**  
+
+The **Domain Name System (DNS)** translates domain names (e.g., google.com) into IP addresses, making it easier to access websites.  
+
+### **8. What is NAT (Network Address Translation)?**  
+
+NAT allows multiple devices on a local network to share a single public IP address for internet access.  
+
+### **9. What is a firewall?**  
+
+A firewall is a security system that monitors and controls incoming and outgoing network traffic based on security rules.  
+
+### **10. What are the types of firewalls?**  
+
+- **Packet Filtering Firewall**  
+- **Stateful Inspection Firewall**  
+- **Proxy Firewall**  
+- **Next-Generation Firewall (NGFW)**  
+
+### **11. What is a VPN?**  
+
+A **Virtual Private Network (VPN)** encrypts internet connections, providing secure remote access and anonymity.  
+
+### **12. What is SSH, and why is it used?**  
+
+SSH (**Secure Shell**) is a protocol used for secure remote access to servers using encrypted communication.  
+
+### **13. What is HTTP and HTTPS?**  
+
+- **HTTP (Hypertext Transfer Protocol)**: Unencrypted web communication.  
+- **HTTPS (HTTP Secure)**: Secure, encrypted communication using SSL/TLS.  
+
+### **14. What is an SSL/TLS certificate?**  
+
+An SSL/TLS certificate encrypts website traffic, ensuring secure communication and trustworthiness.  
+
+### **15. What is a load balancer?**  
+
+A load balancer distributes incoming network traffic across multiple servers to optimize performance and availability.  
+
+### **16. What are different types of load balancers?**  
+
+- **Layer 4 Load Balancer** (Transport Layer)  
+- **Layer 7 Load Balancer** (Application Layer)  
+
+### **17. What is a DMZ in networking?**  
+
+A **Demilitarized Zone (DMZ)** is a security buffer between an internal network and the internet, hosting public-facing services securely.  
+
+### **18. What is port forwarding?**  
+
+Port forwarding redirects network traffic from one port to another, often used to expose internal services externally.  
+
+### **19. What is ARP (Address Resolution Protocol)?**  
+
+ARP translates IP addresses into MAC addresses to enable communication within a local network.  
+
+### **20. What is an IDS and IPS?**  
+
+- **IDS (Intrusion Detection System)**: Monitors network traffic for threats.  
+- **IPS (Intrusion Prevention System)**: Blocks malicious traffic automatically.  
+
+---
+
+## **Intermediate-Level (21-40) Questions**  
+
+### **21. What is Zero Trust Security?**  
+
+Zero Trust is a security model that assumes no entity (inside or outside the network) is trusted by default.  
+
+### **22. What is the difference between symmetric and asymmetric encryption?**  
+
+- **Symmetric Encryption**: Uses one key for encryption and decryption.  
+- **Asymmetric Encryption**: Uses a public-private key pair (e.g., RSA).  
+
+### **23. What is a CDN (Content Delivery Network)?**  
+
+A **CDN** improves website speed and security by distributing content across multiple servers worldwide.  
+
+### **24. What is the difference between TCP and UDP?**  
+
+- **TCP**: Reliable, connection-oriented, ensures data delivery.  
+- **UDP**: Faster, connectionless, best for real-time applications.  
+
+### **25. How does a reverse proxy improve security?**  
+
+A reverse proxy sits between users and backend servers, protecting them from direct exposure and filtering malicious traffic.  
+
+### **26. What are the benefits of HTTPS over HTTP?**  
+
+- Encryption  
+- Data integrity  
+- Authentication  
+
+### **27. How does multi-factor authentication (MFA) enhance security?**  
+
+MFA adds an extra security layer by requiring multiple verification methods (e.g., password + OTP).  
+
+### **28. What is a bastion host?**  
+
+A **bastion host** is a highly secured jump server used to access internal networks securely.  
+
+### **29. What is OSI Model and its layers?**  
+
+The OSI model has **7 layers**: Physical, Data Link, Network, Transport, Session, Presentation, Application.  
+
+### **30. What is a WAF (Web Application Firewall)?**  
+
+A **WAF** protects web applications by filtering and blocking malicious HTTP traffic.  
+
+### **31. What is a honeypot in cybersecurity?**  
+
+A honeypot is a security system designed to detect and study cyberattacks by mimicking real systems.  
+
+### **32. What is BGP (Border Gateway Protocol)?**  
+
+BGP is a routing protocol used for exchanging routing information between networks on the internet.  
+
+### **33. What is DDoS, and how can it be mitigated?**  
+
+A **Distributed Denial-of-Service (DDoS)** attack overwhelms a system. It can be mitigated using rate limiting, firewalls, and cloud-based protection.  
+
+### **34. What is the CIA Triad in security?**  
+
+The **CIA Triad** stands for **Confidentiality, Integrity, and Availability**, which are fundamental security principles.  
+
+### **35. What is SSO (Single Sign-On)?**  
+
+SSO allows users to log in to multiple applications using a single authentication process.  
+
+### **36. What is a security token?**  
+
+A **security token** is a physical or digital device used for authentication.  
+
+### **37. What is an access control list (ACL)?**  
+
+An ACL defines rules that allow or deny traffic based on IP, ports, or protocols.  
+
+### **38. What is a container network security concern?**  
+
+Containers share OS kernels, so misconfigurations can expose services to security threats.  
+
+### **39. What is network segmentation?**  
+
+It is dividing a network into smaller parts to improve security and performance.  
+
+### **40. What is the difference between active and passive reconnaissance?**  
+
+- **Active reconnaissance**: Direct interaction with the target.  
+- **Passive reconnaissance**: Collecting data without direct interaction.  
+
+---
+
+## **Advanced-Level (41-60) Questions**  
+
+### **41. What is mutual TLS (mTLS), and why is it used?**  
+
+Mutual TLS (mTLS) ensures **both client and server** authenticate each other before communication, enhancing security in microservices and API interactions.  
+
+### **42. What is the difference between L3, L4, and L7 firewalls?**  
+
+- **L3 Firewall (Network Layer)**: Filters traffic based on IP addresses.  
+- **L4 Firewall (Transport Layer)**: Filters based on ports and TCP/UDP protocols.  
+- **L7 Firewall (Application Layer)**: Filters based on application-specific data (e.g., HTTP, FTP).  
+
+### **43. How does AWS Security Groups differ from Network ACLs?**  
+
+- **Security Groups**: Act as virtual firewalls at the instance level, stateful.  
+- **Network ACLs**: Act at the subnet level, stateless.  
+
+### **44. What is a SIEM (Security Information and Event Management) system?**  
+
+SIEM aggregates security data from multiple sources to detect, analyze, and respond to threats.  
+
+### **45. What is a threat model in security?**  
+
+Threat modeling identifies potential threats and vulnerabilities in a system to proactively mitigate risks.  
+
+### **46. What is an ephemeral port, and how is it used?**  
+
+Ephemeral ports (e.g., **49152-65535**) are temporary ports used by client applications for outbound connections.  
+
+### **47. How does DNSSEC enhance DNS security?**  
+
+DNSSEC (DNS Security Extensions) prevents DNS spoofing by adding cryptographic signatures to DNS records.  
+
+### **48. What are the different types of VPNs?**  
+
+- **Remote Access VPN** (for individuals connecting to a network remotely).  
+- **Site-to-Site VPN** (connects entire networks).  
+
+### **49. How does a service mesh improve security in Kubernetes?**  
+
+A **service mesh** (e.g., Istio, Linkerd) provides **mTLS, authentication, and observability** for secure communication between microservices.  
+
+### **50. What are some common OWASP Top 10 security risks?**  
+
+1. Injection (e.g., SQL injection)  
+2. Broken Authentication  
+3. Sensitive Data Exposure  
+4. XML External Entities (XXE)  
+5. Broken Access Control  
+6. Security Misconfiguration  
+7. Cross-Site Scripting (XSS)  
+8. Insecure Deserialization  
+9. Using Components with Known Vulnerabilities  
+10. Insufficient Logging & Monitoring  
+
+### **51. How do WebSockets handle security concerns?**  
+
+WebSockets require **authentication, encryption (WSS), and proper origin checks** to prevent attacks.  
+
+### **52. What is an SSRF (Server-Side Request Forgery) attack?**  
+
+An SSRF attack tricks a server into making requests to internal services, leading to data leaks or system compromise.  
+
+### **53. How does an AWS WAF protect applications?**  
+
+AWS WAF filters web traffic based on **rules, rate limiting, and bot mitigation** to prevent common attacks like SQL injection and XSS.  
+
+### **54. How does Kubernetes RBAC (Role-Based Access Control) work?**  
+
+Kubernetes RBAC grants permissions based on **Roles, RoleBindings, ClusterRoles, and ClusterRoleBindings**, restricting access to resources.  
+
+### **55. What is a MAC address, and how does MAC filtering enhance security?**  
+
+A MAC address is a **unique identifier** for network interfaces. MAC filtering allows or denies network access based on these addresses.  
+
+### **56. How does DNS poisoning work, and how can it be prevented?**  
+
+DNS poisoning tricks users into visiting **malicious sites** by altering DNS records. Prevention includes **DNSSEC, monitoring, and secure DNS resolvers**.  
+
+### **57. What is a federated identity in security?**  
+
+Federated identity allows users to authenticate across multiple applications using a **single set of credentials** (e.g., Google or Microsoft sign-in).  
+
+### **58. How does Kubernetes Network Policy improve security?**  
+
+Kubernetes Network Policies define **rules for pod communication**, restricting traffic based on namespaces, labels, and IP ranges.  
+
+### **59. What is the principle of least privilege (PoLP)?**  
+
+PoLP ensures **users and applications only have the minimum access** needed to perform their tasks, reducing security risks.  
+
+### **60. How do HSTS (HTTP Strict Transport Security) and CSP (Content Security Policy) improve web security?**  
+
+- **HSTS**: Forces HTTPS connections to prevent downgrade attacks.  
+- **CSP**: Restricts allowed content sources to prevent XSS attacks.