The nbtstat command is a Windows utility that displays NetBIOS over TCP/IP (NetBT) protocol statistics, NetBIOS name tables, and the NetBIOS name cache. However, the nbtstat command does not support IPv6 addresses, which are the standard format for the Internet Protocol version 6 (IPv6). Therefore, using the nbtstat command with IPv6 addresses will result in an error message or no output. To enumerate NetBIOS names on a network that uses IPv6, you should switch to an enumeration tool that supports IPv6, such as Nmap, which is a network scanning and security auditing tool. Nmap has a scripting engine (NSE) that allows users to write and execute scripts for various network tasks, including NetBIOS enumeration. Nmap can also detect the operating system, services, and vulnerabilities of the target machines, regardless of the IP version they use. References:
* Nbtstat Command - Computer Hope
* Nbtstat CMD: Windows Network Command Line Prompt
* [Nmap Scripting Engine (NSE) Documentation]

Comprehensive and Detailed Explanation:
A TCP SYN flood is a type of Denial of Service (DoS) attack. The attacker sends a barrage of SYN packets with spoofed (random or unreachable) source IP addresses. The victim server replies with SYN/ACK, but the final ACK never arrives.
This results in:
* The victim keeping the half-open connections in the queue.
* The queue filling up, leading to new, legitimate requests being dropped.
From CEH v13 Courseware:
* Module 9: Denial-of-Service Attacks # TCP SYN Flood
Reference:CEH v13 Study Guide - Module 9: TCP Three-Way Handshake and Attack VectorsRFC 4987 - TCP SYN Flooding Attacks and Common Mitigations

Internet Relay Chat (IRC) is a real-time communication protocol. When a client connects to an IRC server, it must first identify itself using two mandatory commands:
* NICK - Specifies the nickname the user wants to use.
* USER - Provides user information such as username, hostname, and real name.
These are the very first commands required to establish presence on the IRC network.
From CEH v13 Official Courseware:
* Module 7: Social Engineering
* Module 19: IoT and Other Emerging Threats (includes botnets and IRC)
CEH v13 Study Guide states:
"When connecting to an IRC server, the client must first send the NICK and USER commands to register the session. Without these, the server will not establish a full connection." Incorrect Options:
* B, C, D: LOGIN and PASS are not valid IRC protocol commands in this context.
Reference:RFC 2812 - Internet Relay Chat: Client Protocol (Section 3.1)CEH v13 Study Guide - Module 19:
IRC Botnet Communications

To secure DNS infrastructure, best practices include:
* B. Harden DNS Servers: Disable unused services, apply patches, implement secure configurations.
* C. Use Split-Horizon DNS: Present different DNS data to internal vs. external users to prevent data leakage.
* D. Restrict Zone Transfers: Prevent unauthorized replication of zone data using IP-based access control or TSIG.
* E. Subnet Diversity: Place DNS servers on different subnets or networks to enhance resilience.
From CEH v13 Official Courseware:
* Module 3: Scanning Networks
* Module 20: Cryptography
Incorrect Option:
* A: Hosting DNS on multi-purpose servers increases the attack surface and violates security best practices.
Reference:CEH v13 Study Guide - Module 3: DNS Hardening & Zone Transfer SecurityNIST SP 800-81r2 - Secure Domain Name System Deployment Guide

In CEH v13 Module 05: System Hacking, and Module 14: Access Control, Identity Management, and Cryptography, Single Sign-On (SSO) is defined as a system that allows users to authenticate once and gain access to multiple systems without re-entering credentials.
SSO uses a Central Authentication Server (CAS).
Common technologies: Kerberos, OAuth, SAML, AD Federation Services.
Improves user convenience and centralized credential management.
Reference:
CEH v13 Module 14 - Identity and Access Management Concepts
CEH iLabs: SSO Architecture Demonstration