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Computer Networks · Question Set
Network Security & Cryptography interview questions for placements and exams.
Questions
13
Included in this set
Subject
Computer Networks
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Difficulty
Mixed
Level of this set
Go through each question and its explanation. Use this set as a focused practice pack for Computer Networks.
Network security focuses on protecting data as it travels through a network. It ensures confidentiality (preventing unauthorized access), integrity (preventing unauthorized modification), and availability (ensuring access when needed). These three principles form the CIA triad — the foundation of cybersecurity.
For complete preparation, combine this set with full subject-wise practice for Computer Networks. You can also explore other subjects and sets from the links below.
Network security policies define the rules and procedures for protecting organizational assets. They include password policies, access control lists, data handling guidelines, and incident response procedures. These policies ensure consistent security behavior and compliance with standards like ISO 27001 or GDPR. Interviewers appreciate when you connect policies to practical enforcement mechanisms like firewalls and monitoring systems.
Encryption is the process of converting plaintext into ciphertext to protect it from unauthorized access. Only authorized users with the correct key can decrypt and read the data. It is essential for secure communication across untrusted networks like the Internet.
A firewall monitors and controls incoming and outgoing network traffic using predefined security rules. It acts as a barrier between trusted and untrusted networks, protecting against unauthorized access and attacks. Firewalls can be hardware, software, or both.
Secure Sockets Layer (SSL) and Transport Layer Security (TLS) provide end-to-end encryption for web traffic. They ensure that data exchanged between a web browser and server remains confidential and tamper-proof. Modern browsers use TLS, the successor to SSL.
A VPN creates an encrypted tunnel between the user’s device and a remote server over the public Internet. It masks the user’s IP address and secures data from eavesdroppers. VPNs are widely used for remote work, secure browsing, and bypassing geo-restrictions. In interviews, explain how VPNs use encryption and tunneling protocols like IPSec or OpenVPN to provide confidentiality and integrity.
Hashing converts data into a fixed-length digest using algorithms like SHA or MD5. It is used to detect unauthorized modifications. Even small changes in input produce a different hash, making it ideal for verifying file integrity or storing passwords securely.
A DoS attack overwhelms a target system with excessive traffic, making it unavailable to legitimate users. Distributed DoS (DDoS) attacks amplify this by using multiple compromised systems. Defense strategies include rate limiting, firewalls, load balancing, and using anti-DDoS services. In interviews, discuss both preventive measures and detection tools like intrusion detection systems or content delivery networks.
A Certificate Authority (CA) verifies the identity of entities (users, websites, or organizations) and issues digital certificates to prove their authenticity. PKI relies on trusted CAs to ensure secure communication across networks like HTTPS.
IPSec secures IP communication by authenticating and encrypting each IP packet in a communication session. It operates at the network layer and supports VPNs, ensuring confidentiality, data integrity, and origin authentication.
In a MITM attack, an attacker secretly intercepts and alters communication between two parties without their knowledge. They can steal credentials or inject malicious data. Encryption protocols like SSL/TLS prevent this by ensuring both parties exchange data securely with verified identities. Always mention mutual authentication and certificate validation as key defenses during interviews.
Symmetric encryption uses the same key for both encryption and decryption, making it fast and efficient. Examples include AES and DES. However, key distribution is a challenge because both parties must securely share the same key. Asymmetric encryption uses a public key for encryption and a private key for decryption. It is slower but solves the key distribution problem. RSA and ECC are common examples. In practice, systems combine both—using asymmetric encryption to exchange symmetric session keys.
An IDS detects and alerts administrators about suspicious activities, while an IPS goes a step further by automatically taking action to block or prevent attacks. Both systems are essential for layered network defense.