CISSP Communication and Network Security — Timed 15 Questions

Question 1

A security analyst observes a network attack where an attacker sends forged ARP messages to associate the attacker's MAC address with the IP address of the default gateway. This attack occurs at which layer of the OSI model?

Accepted Answer

Layer 2 – Data Link. ARP operates at Layer 2 (Data Link) because it maps IP addresses (Layer 3) to MAC addresses (Layer 2) and is encapsulated directly within an Ethernet frame, not an IP packet. The attack described—ARP spoofing—forges ARP replies to poison the target's ARP cache, which is a Layer 2 function. Therefore, the attack occurs at Layer 2 of the OSI model.

Answer

Layer 3 – Network

Answer

Layer 1 – Physical

Answer

Layer 4 – Transport

Question 2

An organization is deploying a VPN solution for remote employees. The security team requires a modern protocol with perfect forward secrecy, uses elliptic curve cryptography, and is known for its efficient, minimal codebase. Which VPN protocol should they choose?

Accepted Answer

WireGuard. WireGuard is the correct choice because it is a modern VPN protocol that uses elliptic curve cryptography (Curve25519) for key exchange, provides perfect forward secrecy by default through its ephemeral session keys, and is designed with a minimal, auditable codebase (around 4,000 lines) for efficiency and security. These features directly match the organization's requirements for a modern protocol with PFS, ECC, and a lean implementation.

Answer

L2TP/IPsec

Answer

PPTP

Answer

IPsec with IKEv2

Question 3

A security engineer is configuring a firewall that makes decisions based on source/destination IP addresses and port numbers without tracking the state of connections. Which type of firewall is this?

Accepted Answer

Packet filter firewall. A packet filter firewall operates at Layers 3 and 4 of the OSI model, making forwarding decisions solely based on static fields such as source/destination IP addresses and port numbers. It does not maintain any connection state table, meaning each packet is evaluated independently without reference to previous packets. This stateless behavior is the defining characteristic that distinguishes it from stateful inspection firewalls.

Answer

Stateful inspection firewall

Answer

Application proxy firewall

Answer

Next-generation firewall

Question 4

During a security assessment, a penetration tester sends TCP SYN packets to various ports on a target server. Based on the responses, the tester determines which ports are open. This technique is commonly used at which OSI layer?

Accepted Answer

Layer 4 – Transport. The TCP SYN scan operates at Layer 4 (Transport) of the OSI model because it manipulates TCP segment headers, specifically the SYN flag, to probe port states. The tester sends SYN packets and interprets the response (SYN-ACK for open, RST for closed) to infer port availability, which is a transport-layer function defined by RFC 793.

Answer

Layer 7 – Application

Answer

Layer 3 – Network

Answer

Layer 2 – Data Link

Question 5

An organization wants to secure email communications by providing encryption and digital signatures. They require a solution that uses a web of trust model rather than a hierarchical PKI. Which protocol should they implement?

Accepted Answer

PGP/GPG. PGP/GPG implements a web of trust model where users sign each other's keys to establish trust, rather than relying on a centralized Certificate Authority (CA). It provides both encryption and digital signatures for email, making it the correct choice for an organization that explicitly wants to avoid hierarchical PKI.

Answer

S/MIME

Answer

TLS

Answer

SSH

Question 6

A network administrator is configuring SNMPv3 for monitoring network devices. The organization requires both authentication and encryption of SNMP traffic. Which combination of protocols should be used to meet this requirement?

Accepted Answer

SHA for authentication, AES for privacy. SNMPv3 supports both authentication and encryption via separate User-based Security Model (USM) parameters. To meet the requirement for both, you must select an authentication protocol (e.g., SHA) and a privacy (encryption) protocol (e.g., AES). Option C correctly pairs SHA for authentication with AES for privacy, providing integrity verification and confidentiality of SNMP messages.

Answer

MD5 for authentication, no privacy

Answer

SHA for authentication, no privacy

Answer

MD5 for authentication, DES for privacy

Question 7

Which wireless security protocol replaces the pre-shared key (PSK) authentication with Simultaneous Authentication of Equals (SAE) to provide stronger security and forward secrecy?

Accepted Answer

WPA3. WPA3 replaces the Pre-Shared Key (PSK) authentication used in WPA2 with Simultaneous Authentication of Equals (SAE), defined in IEEE 802.11-2016 and specified in RFC 7664. SAE provides forward secrecy by using a Diffie-Hellman key exchange that ensures even if the long-term password is compromised, past session keys remain secure. This eliminates vulnerabilities to offline dictionary attacks that plague WPA2-PSK.

Answer

WEP

Answer

WPA2 with TKIP

Answer

WPA2 with CCMP

Question 8

A security analyst discovers an attack where an attacker sets up a rogue wireless access point with a legitimate SSID to trick users into connecting. Once connected, the attacker captures credentials. This type of attack is known as:

Accepted Answer

Evil twin attack. This is an evil twin attack because the attacker creates a rogue access point that broadcasts the same SSID as a legitimate network, tricking users into connecting to it. Once connected, the attacker can capture credentials or other sensitive data by acting as a man-in-the-middle. The key differentiator is the impersonation of a legitimate SSID to deceive users, not just the presence of an unauthorized AP.

Answer

Deauthentication attack

Answer

Rogue AP attack

Answer

Karma attack

Question 9

An organization is implementing network segmentation. They need to place publicly accessible servers (e.g., web and email) in a separate network that is isolated from the internal LAN but still allows controlled access from the internet. Which architecture should they use?

Accepted Answer

DMZ. A DMZ (demilitarized zone) is a network segment that sits between the internet and the internal LAN, hosting publicly accessible servers like web and email. It uses firewall rules to allow inbound traffic from the internet to the DMZ servers while blocking direct access to the internal network, and typically permits only specific outbound responses or updates from the DMZ to the internal LAN. This architecture provides the isolation and controlled access required by the scenario.

Answer

Micro-segmentation

Answer

VPN

Answer

VLAN

Question 10

A company deploys DNSSEC to protect its DNS infrastructure. Which cryptographic operation does DNSSEC primarily use to ensure the authenticity and integrity of DNS data?

Accepted Answer

Digital signatures of DNS records. DNSSEC primarily uses digital signatures to ensure the authenticity and integrity of DNS data. Each DNS zone is signed with a private key, and resolvers verify the signatures using the corresponding public key, which is published as a DNSKEY record. This process allows the resolver to cryptographically confirm that the data has not been modified in transit and originates from the authoritative source.

Answer

Hashing of DNS responses without keys

Answer

Transport Layer Security for DNS

Answer

Symmetric encryption of DNS queries

Question 11

Which of the following is a key feature of TLS 1.3 that enhances security compared to earlier versions?

Accepted Answer

Mandatory forward secrecy. TLS 1.3 mandates forward secrecy by requiring ephemeral Diffie-Hellman (DHE or ECDHE) key exchange for all sessions, eliminating static RSA and static DH key exchanges. This ensures that even if the server's long-term private key is compromised, past session keys cannot be derived, protecting historical traffic. Earlier TLS versions allowed static key exchanges, making them vulnerable to retrospective decryption.

Answer

Support for RC4 encryption

Answer

Support for DES and 3DES

Answer

Use of static RSA key exchange

Question 12

A security architect is designing a zero-trust network. Which principle is fundamental to a zero-trust architecture (ZTA) such as BeyondCorp?

Accepted Answer

Never trust, always verify. In a zero-trust architecture (ZTA) like Google's BeyondCorp, the foundational principle is 'never trust, always verify.' This means no entity—user, device, or network—is trusted by default, regardless of its location (inside or outside the corporate perimeter). Every access request must be authenticated, authorized, and continuously validated before granting access to resources, eliminating implicit trust based on network location.

Answer

Trust but verify

Answer

Trust internal users implicitly

Answer

Trust network location as a primary factor

Question 13

A network engineer is configuring an IPsec VPN in tunnel mode. Which IPsec protocol provides both authentication and encryption of the entire IP packet?

Accepted Answer

ESP (Encapsulating Security Payload). ESP (Encapsulating Security Payload) in tunnel mode provides both authentication and encryption for the entire original IP packet, including the original header and payload. It encapsulates the packet with a new IP header and ESP trailer, ensuring confidentiality via encryption and integrity via authentication. This makes it the correct choice for a VPN requiring both security services.

Answer

IKE (Internet Key Exchange)

Answer

ISAKMP

Answer

AH (Authentication Header)

Question 14

Which type of firewall is capable of inspecting application-layer data, performing SSL decryption, and integrating intrusion prevention capabilities?

Accepted Answer

Next-generation firewall. A next-generation firewall (NGFW) goes beyond traditional stateful inspection by incorporating deep packet inspection (DPI) of application-layer data, the ability to decrypt and inspect SSL/TLS traffic, and integrated intrusion prevention system (IPS) capabilities. This convergence allows NGFWs to identify and block threats within encrypted sessions and enforce policies based on application identity rather than just ports and protocols.

Answer

Packet filter firewall

Answer

Application proxy firewall

Answer

Stateful firewall

Question 15

A company uses SSH for remote administration. To enhance security, they want to implement public-key authentication. Which statement about SSH public-key authentication is true?

Accepted Answer

The private key must be kept secret by the user. In SSH public-key authentication, the private key is the secret half of the asymmetric key pair and must be kept confidential by the user. The server stores only the public key, and authentication is proven by the client signing a challenge with the private key, which the server verifies using the stored public key. This ensures that even if the server is compromised, the private key remains safe on the client side.

Answer

The public key is used to decrypt the session

Answer

Public-key authentication does not require a passphrase

Answer

The private key is stored on the server