The correct answer is C. Firewalls and IPS systems protect the perimeter, but they do not replace system hardening, access control, patching, auditing, and regular security testing on the internal network elements themselves. In CEH security concepts, defense should be implemented in layers, commonly called defense-in- depth. This means that even if an attacker bypasses perimeter defenses, internal systems should still be protected.
Because these network elements are Linux-based computers, they require strong user account management, secure authentication, least privilege, service hardening, vulnerability assessment, patch management, logging, and periodic audits. Strong passwords and unique user IDs also support accountability and reduce the risk of unauthorized access.
Option A is incorrect because relying only on firewalls and IPS creates a single point of failure. Option B mentions disaster recovery but does not address preventive security. Option D is also incomplete because physical security alone cannot stop remote attacks, malware, insider threats, misconfigurations, or credential abuse.
Therefore, the best policy is to harden the systems and perform regular security testing and audits.

CEH documentation explains that WPA-TKIP was a transitional security protocol and does not use AES encryption, relying instead on RC4-based mechanisms.
The lack of AES-based encryption makes WPA-TKIP vulnerable to injection and replay attacks.
Option C is correct.
Options A applies to WEP.
Option B affects authentication, not TKIP weakness.
Option D is not the primary TKIP flaw.
CEH recommends WPA2/WPA3 with AES.

UDP scanning produces reliable "closed" results only when an ICMP Port Unreachable is returned. Silent responses indicate either open ports (no reply expected) or filtered ports (blocks dropping packets). CEH emphasizes that non-responses require retransmission or alternate verification techniques.

The correct answer is A. LDAP Injection.
The scenario describes malicious input being inserted into directory-based search logic used to validate identities. LDAP is commonly used for centralized directory authentication and account lookups. When user input is embedded directly into LDAP filters without proper validation, an attacker can alter the filter logic using operators, wildcards, and special LDAP syntax.
CEH-aligned material states that LDAP injection takes advantage of non-validated input and that an attacker may access information by using an LDAP filter to search the directory database . Another CEH exam reference explains that LDAP injection exploits applications that construct LDAP statements based on user input and pass that input directly into LDAP queries .
Option B. OS Command Injection is incorrect because the scenario does not involve operating system commands.
Option C. SQL Injection is incorrect because the backend lookup is directory-based, not relational database SQL.
Option D. XPath Injection is incorrect because XPath injection targets XML query expressions, not LDAP directory filters.
Therefore, the best answer is A. LDAP Injection.

According to CEH v13 Social Engineering, social engineering attacks manipulate human trust rather than technical vulnerabilities. Option A describes a classic pretexting attack, where the attacker impersonates IT staff and fabricates a false issue to trick a victim into revealing credentials.
This scenario aligns perfectly with CEH definitions because:
The attacker relies on authority impersonation
The victim is socially manipulated
No technical exploitation is required
Option B is a legitimate security activity.
Option C is accidental malware introduction, not social engineering.
Option D is physical negligence exploitation, not direct social engineering interaction.
CEH v13 stresses that pretexting attacks are extremely effective against new employees who lack familiarity with procedures. Therefore, Option A is correct.