CNSP Leak Questions

In Linux, password hashes are stored in a secure file to protect user authentication data. The evolution of Linux security practices moved password storage from plaintext or weakly protected files to a more secure location.

Why C is correct:The /etc/shadow file is the standard location for storing password hashes in modern Linux systems. This file is readable only by the root user, enhancing security by restricting access. It contains encrypted password hashes (typically using algorithms like SHA-512), along with user details such as password expiration policies. CNSP documentation on Linux security emphasizes /etc/shadow as the authoritative source for password hashes, replacing older methods.

Why other options are incorrect:

A. /etc/passwd:Historically, /etc/passwd stored passwords in plaintext or weakly hashed forms (e.g., using DES), but modern systems use it only for user account information (e.g., UID, GID, home directory) and reference /etc/shadow for hashes.

B. /etc/password:This is not a valid file in the Linux file system; it appears to be a typographical error or misunderstanding, with no recognized role in password storage.

D. /usr/bin/shadow:/usr/bin contains executable binaries, not configuration or data files like password hashes. /etc/shadow is the correct path.

References:CNSP "Linux Authentication Mechanisms" (Section on Password Storage) details the transition to /etc/shadow for enhanced security and contrasts it with /etc/passwd.

TCP (Transmission Control Protocol) and UDP (User Datagram Protocol) port numbers are defined by a 16-bit field in their packet headers, as specified in RFC 793 (TCP) and RFC 768 (UDP). A 16-bit integer ranges from 0 to 65,535, yielding a total of 65,536 possible ports (2^16). However,port 0is universally reserved across both protocols and is not considered "usable" for standard network communication. According to the Internet Assigned Numbers Authority (IANA), port 0 is designated for special purposes, such as indicating an invalid or dynamic port assignment in some systems (e.g., when a client requests an ephemeral port). In practice, operating systems and applications avoid binding to port 0 for listening services, and it’s often used in error conditions or as a placeholder in protocol implementations (e.g., socket programming).

Thus, theusable port rangespans from 1 to 65,535, totaling 65,535 ports. These ports are categorized by IANA into:

Well-Known Ports (0–1023):Reserved for system services (e.g., HTTP on 80/TCP). Note that 0 is still reserved within this range.

Registered Ports (1024–49151):Assigned to user applications.

Dynamic/Ephemeral Ports (49152–65535):Used temporarily by clients.

From a security perspective, understanding the usable port count is critical for firewall configuration, port scanning (e.g., with Nmap), and detecting anomalies (e.g., services binding to unexpected ports). Misconfiguring a system to use port 0 could lead to protocol errors or expose vulnerabilities, though it’s rare. The CNSP curriculum likely emphasizes this distinction to ensure practitioners can accurately scope network security assessments.

Why other options are incorrect:

A. 65536:This reflects the total number of possible ports (0–65535), but it includes the reserved port 0, which isn’t usable for typical TCP/UDP communication. In security contexts, including port 0 in a count could lead to misconfigured rules or scanning errors.

C. 63535:This is an arbitrary number with no basis in the 16-bit port structure. It might stem from a typo or misunderstanding (e.g., subtracting 2000 from 65535 incorrectly), but it’s invalid.

D. 65335:Similarly, this lacks grounding in protocol standards. It could be a miscalculation (e.g., subtracting 200 from 65535), but it doesn’t align with TCP/UDP specifications.

Real-World Context:In penetration testing, tools like Nmap scan ports 1–65535 by default, excluding 0 unless explicitly specified (e.g., -p0-65535), reinforcing that 65,535 is the practical usable count.References:CNSP Official Study Guide (Network Protocols and Ports); RFC 793 (TCP), RFC 768 (UDP), IANA Service Name and Transport Protocol Port Number Registry.

A DNS zone transfer involves replicating the DNS zone data (e.g., all records for a domain) from a primary to a secondary DNS server, requiring a reliable transport mechanism.

Why A is correct:DNS zone transfers use TCP port 53 because TCP ensures reliable,ordered delivery of data, which is critical for transferring large zone files. CNSP notes that TCP is the standard protocol for zone transfers (e.g., AXFR requests), as specified in RFC 5936.

Why other options are incorrect:

B. 53/UDP:UDP port 53 is used for standard DNS queries and responses due to its speed and lower overhead, but it is not suitable for zone transfers, which require reliability over speed.

C. Both 1 and 2:This is incorrect because zone transfers are exclusively TCP-based, not UDP-based.

D. None of the above:Incorrect, as 53/TCP is the correct port for DNS zone transfers.

References:CNSP "DNS Security Practices" (Section on Zone Transfers) specifies TCP port 53 as the protocol for secure and reliable zone transfer operations.

Online attacks require real-time interaction with a target system (e.g., a login interface), whereas offline attacks occur without direct system interaction, typically after obtaining data like password hashes. A rainbow table attack is an offline method that uses precomputed tables of hash values to reverse-engineer passwords from stolen hash databases, distinguishing it from the other options, which are online.

Why B is correct:Rainbow table attacks are performed offline after an attacker has already acquired a hash (e.g., from a compromised database). The attacker matches the hash against precomputed tables to find the plaintext password, requiring no interaction with the target system during the attack. CNSP classifies this as an offline password recovery technique.

Why other options are incorrect:

A:Brute force attacks involve repeatedly submitting password guesses to a live system (e.g., via SSH or a web login), making it an online attack.

C:Password spraying attacks test a few common passwords across many accounts on a live system, also an online attack aimed at avoiding lockouts.

D:Phishing attacks trick users into submitting credentials through fake interfaces (e.g., emails or websites), requiring real-time interaction and thus classified as online.

References:CNSP "Password Attack Methodologies" (Section on Online vs. Offline Attacks) defines rainbow table attacks as offline and contrasts them with online methods like brute force and phishing.