CNSP Exam Dumps : Certified Network Security Practitioner (CNSP)

EternalBlue(MS17-010) is an exploit targeting a buffer overflow in Microsoft’s SMB (Server Message Block) implementation, leaked by the Shadow Brokers in 2017. SMB enables file/printer sharing:

SMBv1 (1980s):Legacy, used in Windows NT/XP.

SMBv2 (2006, Vista):Enhanced performance/security.

SMBv3 (2012, Windows 8):Adds encryption, multichannel.

Vulnerability:

EternalBlue exploits a flaw inSMBv1’s SRVNET driver (srv.sys), allowing remote code execution via crafted packets. Microsoft patched it in March 2017 (MS17-010).

Affected OS: Windows XP to Server 2016 (pre-patch), if SMBv1 enabled.

Proof: WannaCry/NotPetya used it, targeting port 445/TCP.

Version Scope:

SMBv1 Only:The bug resides in SMBv1’s packet handling (e.g., TRANS2 requests). SMBv2/v3 rewrote this code, immune to the specific overflow.

Microsoft: Post-patch, SMBv1 is disabled by default (Windows 10 1709+).

Security Implications:CNSP likely stresses disabling SMBv1 (e.g., via Group Policy) and patching, as EternalBlue remains a threat in legacy environments.

Why other options are incorrect:

B, C:SMBv2/v3 aren’t vulnerable; the flaw is SMBv1-specific.

D:SMBv2 isn’t affected, only SMBv1.

Real-World Context:WannaCry’s 2017 rampage hit unpatched SMBv1 systems (e.g., NHS), costing billions.References:CNSP Official Documentation (Windows Exploits); Microsoft MS17-010 Bulletin.

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.

DDoS (Distributed Denial of Service) attacks aim to overwhelm a target’s resources with excessive traffic, disrupting availability, whereas other attack types target different goals.

Why D is correct:Brute force attacks focus on guessing credentials (e.g., passwords) to gain unauthorized access, not on denying service. CNSP classifies it as an authentication attack, not a DDoS method.

Why other options are incorrect:

A:SYN Flood exhausts TCP connection resources, a classic DDoS attack.

B:NTP Amplification leverages amplified responses to flood targets, a DDoS technique.

C:UDP Flood overwhelms a system with UDP packets, another DDoS method.

References:CNSP "DDoS Attack Types" (Section on Attack Classification) excludes brute force from DDoS categories, listing SYN, NTP, and UDP floods as examples.