https://en.wikipedia.org/wiki/Meet-in-the-middle_attack
The meet-in-the-middle attack (MITM), a known plaintext attack, is a generic space-time tradeoff cryptographic attack against encryption schemes that rely on performing multiple encryption operations in sequence. The MITM attack is the primary reason why Double DES is not used and why a Triple DES key (168-bit) can be bruteforced by an attacker with 256 space and 2112 operations.
The intruder has to know some parts of plaintext and their ciphertexts. Using meet-in-the-middle attacks it is possible to break ciphers, which have two or more secret keys for multiple encryption using the same algorithm. For example, the 3DES cipher works in this way. Meet-in-the-middle attack was first presented by Diffie and Hellman for cryptanalysis of DES algorithm.

DNS uses Ports 53 which is almost always open on systems, firewalls, and clients to transmit DNS queries.
instead of the more familiar Transmission Control Protocol (TCP) these queries use User Datagram Protocol (UDP) due to its low-latency, bandwidth and resource usage compared TCP-equivalent queries. UDP has no error or flow-control capabilities, nor does it have any integrity checking to make sure the info arrived intact.
How is internet use (browsing, apps, chat etc) so reliable then? If the UDP DNS query fails (it's a best-effort protocol after all) within the first instance, most systems will retry variety of times and only after multiple failures, potentially switch to TCP before trying again; TCP is additionally used if the DNS query exceeds the restrictions of the UDP datagram size - typically 512 bytes for DNS but can depend upon system settings.
Figure 1 below illustrates the essential process of how DNS operates: the client sends a question string (for example, mail.google[.]com during this case) with a particular type - typically A for a number address. I've skipped the part whereby intermediate DNS systems may need to establish where '.com' exists, before checking out where 'google[.]com' are often found, and so on.
Many worms and scanners are created to seek out and exploit systems running telnet. Given these facts, it's really no surprise that telnet is usually seen on the highest Ten Target Ports list. Several of the vulnerabilities of telnet are fixed. They require only an upgrade to the foremost current version of the telnet Daemon or OS upgrade. As is usually the case, this upgrade has not been performed on variety of devices. this might flow from to the very fact that a lot of systems administrators and users don't fully understand the risks involved using telnet. Unfortunately, the sole solution for a few of telnets vulnerabilities is to completely discontinue its use. the well-liked method of mitigating all of telnets vulnerabilities is replacing it with alternate protocols like ssh. Ssh is capable of providing many of an equivalent functions as telnet and a number of other additional services typical handled by other protocols like FTP and Xwindows. Ssh does still have several drawbacks to beat before it can completely replace telnet. it's typically only supported on newer equipment. It requires processor and memory resources to perform the info encryption and decryption. It also requires greater bandwidth than telnet thanks to the encryption of the info . This paper was written to assist clarify how dangerous the utilization of telnet are often and to supply solutions to alleviate the main known threats so as to enhance the general security of the web Once a reputation is resolved to an IP caching also helps: the resolved name-to-IP is usually cached on the local system (and possibly on intermediate DNS servers) for a period of your time . Subsequent queries for an equivalent name from an equivalent client then don't leave the local system until said cache expires. Of course, once the IP address of the remote service is understood , applications can use that information to enable other TCP-based protocols, like HTTP, to try to to their actual work, for instance ensuring internet cat GIFs are often reliably shared together with your colleagues.
So, beat all, a couple of dozen extra UDP DNS queries from an organization's network would be fairly inconspicuous and will leave a malicious payload to beacon bent an adversary; commands could even be received to the requesting application for processing with little difficulty.

The correct answer is C, Bypass filters. In wireless network security, access points may use MAC address filtering to allow only devices whose MAC addresses are listed in the access point's whitelist. CEH wireless- hacking material explains that MAC spoofing can be used to change a wireless adapter's MAC address so it matches an allowed MAC address in the access point's whitelist, thereby bypassing the MAC filter. This does not provide encryption, because encryption protects data confidentiality using cryptographic algorithms. It is also not IDS, because an intrusion detection system monitors and alerts on suspicious activity. Logging records events and activities, which is unrelated to changing a MAC address. MAC spoofing is an impersonation technique: the attacker observes or obtains a valid MAC address and configures their own interface to use it. Therefore, in the context of CEH wireless attacks and access control weaknesses, MAC spoofing is primarily used to bypass MAC-based access filters.

ARP (Address Resolution Protocol) spoofing/poisoning is a common attack in which an attacker sends falsified ARP messages to associate their MAC address with the IP address of another host. To defend against ARP spoofing:
* A. Port Security: Limits the number of MAC addresses per port; prevents MAC flooding and spoofing.
* B. ARPwatch: Monitors ARP traffic and alerts on unusual changes.
* D. Static ARP Entries: Prevent ARP responses from overwriting MAC-IP mappings, effective in small networks.
From CEH v13 Official Courseware:
* Module 8: Sniffing
* Module 11: Session Hijacking
* Module 20: Network Security
Incorrect Options:
* C: Firewalls operate at Layer 3+; ARP is a Layer 2 protocol, so firewalls don't prevent ARP spoofing.
* E: Static IP addresses do not prevent ARP poisoning.
Reference:CEH v13 Study Guide - Module 8: ARP Spoofing Mitigation TechniquesNIST SP 800-115 - Technical Guide to Information Security Testing and Assessment

A keylogger is a type of spyware that can record and steal consecutive keystrokes (and much more) that the user enters on a device. Keyloggers are a common tool for cybercriminals, who use them to capture passwords, credit card numbers, personal information, and other sensitive data. Keyloggers can be installed on a device through various methods, such as phishing emails, malicious downloads, or physical access. To confirm the type of program, the security team can use a web search tool, such as Bing, to look for keylogger programs and compare their features and behaviors with the suspicious program they encountered.
Alternatively, they can use a malware analysis tool, such as Malwarebytes, to scan and identify the program and its characteristics.
To prevent the same attack from occurring in the future, the security team should employ intrusion detection systems (IDS) and regularly update the system software. An IDS is a system that monitors network traffic and system activities for signs of malicious or unauthorized behavior, such as keylogger installation or communication. An IDS can alert the security team of any potential threats and help them respond accordingly. Regularly updating the system software can help patch any vulnerabilities or bugs that keyloggers may exploit to infect the device. Additionally, the security team should also remove the keylogger program from the affected computers and change any compromised passwords or credentials. References:
* Keylogger | What is a Keylogger? How to protect yourself
* How to Detect and Remove a Keylogger From Your Computer
* Intrusion Detection Systems (IDS) and Intrusion Prevention Systems (IPS)
* What is a Keylogger? | Keystroke Logging Definition | Avast
* Keylogger Software: 11 Best Free to Use in 2023