Network & Security Interview Questions

What to Expect in a Network & Security Interview

Network and security questions appear in nearly every infrastructure, DevOps, and backend engineering interview — and they're increasingly common in full-stack and cloud roles too. These questions test your understanding of how data moves across networks, how systems are secured, and how common attack vectors are detected and mitigated.

The 6 core areas you'll be tested on:

• Networking Fundamentals — TCP vs. UDP, the OSI model, DNS resolution, HTTP/2 and HTTP/3, subnetting and CIDR notation. You need to be able to trace a packet from client to server and explain what happens at each layer.
• Firewalls & Intrusion Detection — Stateful vs. stateless firewalls, packet filtering rules, IDS vs. IPS, network segmentation. Know when to use a WAF (Web Application Firewall) vs. a traditional network firewall.
• Encryption & TLS — Symmetric vs. asymmetric encryption, how TLS handshakes work, certificate chains and PKI, perfect forward secrecy. Be able to explain why HTTPS matters and what can go wrong with certificate pinning.
• Authentication & Authorization — OAuth 2.0 flows, JWT token structure and vulnerabilities, SAML vs. OIDC, multi-factor authentication, session management. This overlaps heavily with backend interview questions.
• Common Attack Vectors — SQL injection, XSS (stored vs. reflected), CSRF, man-in-the-middle, DNS spoofing, phishing. For each attack, know the mechanism, real-world examples, and the defense.
• Penetration Testing — Reconnaissance techniques, exploitation methodology, OWASP Top 10, reporting and remediation. Companies like Stripe and PayPal place heavy emphasis on security knowledge in their engineering interviews.

How to study: Start with the fundamentals (TCP/IP, OSI model) before moving to attacks and defenses. The questions below are ordered by topic, not difficulty — work through them in order for a natural learning progression. For system-level security architecture, pair this with our System Design Playbook and OS & Database questions.