Banner grabbing is used to extract version information from services, including SSH, FTP, and web servers.
Option A (Network sniffing) ❌: Captures packets, but does not directly reveal service versions.
Option B (IP scanning) ❌: Identifies active hosts, but not SSH versions.
Option C (Banner grabbing) ✅: Correct.
Can be performed with:
nc <target> 22
or
telnet <target> 22
Option D (DNS enumeration) ❌: Retrieves domain name records, not SSH versions.
Reference: CompTIA PenTest+ PT0-003 Official Guide - Service Enumeration & Banner Grabbing

Testing with proof-of-concept code from an exploit database is the best method to support validation of the possible findings, as it will demonstrate whether the CVEs are actually exploitable on the target VoIP call manager. Proof-of-concept code is a piece of software or script that shows how an attacker can exploit a vulnerability in a system or application. An exploit database is a repository of publicly available exploits, such as Exploit Database or Metasploit.
Reference: https://dokumen.pub/hacking-exposed-unified-communications-amp-voip-security-secrets-amp- solutions-2nd-edition-9780071798778-0071798773-9780071798761-0071798765.html

Password spraying is a type of password guessing attack that involves trying one or a few common passwords against many usernames or accounts. Password spraying can avoid account lockout policies that limit the number of failed login attempts per account by spreading out the attempts over time and across different accounts. Password spraying can also increase the chances of success by using passwords that are likely to be used by many users, such as default passwords, seasonal passwords, or company names. Mask is a type of password cracking attack that involves using a mask or a pattern to generate passwords based on known or guessed characteristics of the password, such as length, case, or symbols. Rainbow is a technique of storing precomputed hashes of passwords in a table that can be used to quickly crack passwords by looking up the hashes. Dictionary is a type of password cracking attack that involves using a wordlist or a dictionary of common or likely passwords to try against an account.

data structures are used to store data in an organized form, and some data structures are more efficient and suitable for certain operations than others. For example, hash tables, skip lists and jump lists are some dictionary data structures that can insert and access elements efficiently3.
For string comparison, there are different algorithms that can measure how similar two strings are, such as Levenshtein distance, Hamming distance or Jaccard similarity4. Some of these algorithms can be implemented using data structures such as arrays or hashtables5.

Providing a detailed list of all changes allows the customer to verify and confirm that systems have been properly restored to their original state, ensuring accountability and completeness in cleanup.