Gathering Wordlist from the Target Website An attacker uses the CeWL tool to gather a list of words from the target website and perform a brute-force attack on the email addresses gathered earlier. # Cewl www.
certifiedhacker.com (P.200/184)

Agent-based scanners reside on a single machine but can scan several machines on the same network.
Network-based scanner
A network-based vulnerability scanner, in simplistic terms, is the process of identifying loopholes on a computer's network or IT assets, which hackers and threat actors can exploit. By implementing this process, one can successfully identify their organization's current risk(s). This is not where the buck stops; one can also verify the effectiveness of your system's security measures while improving internal and external defenses. Through this review, an organization is well equipped to take an extensive inventory of all systems, including operating systems, installed software, security patches, hardware, firewalls, anti-virus software, and much more.
Agent-based scanner
Agent-based scanners make use of software scanners on each and every device; the results of the scans are reported back to the central server. Such scanners are well equipped to find and report out on a range of vulnerabilities.
NOTE: This option is not suitable for us, since for it to work, you need to install a special agent on each computer before you start collecting data from them.

The best practice to meet the client's requirement is to encrypt data client-side before uploading to the cloud and retain control of the encryption keys. This practice is also known as client-side encryption or end-to-end encryption, and it involves encrypting the data on the client's device using a software or hardware tool that generates and manages the encryption keys. The encrypted data is then uploaded to the cloud service, where it remains encrypted at rest. The encryption keys are never shared with the cloud service provider or any third party, and they are only used by the client to decrypt the data when needed. This way, the client can maintain full control over the encryption keys and the security of the data, even when the data is stored on a public cloud service12.
The other options are not as optimal as option D for the following reasons:
* A. Use the cloud service provider's encryption services but store keys on-premises: This option is not feasible because it contradicts the client's requirement of maintaining full control over the encryption keys. Using the cloud service provider's encryption services means that the client has to rely on the cloud service provider to generate and manage the encryption keys, even if the keys are stored on- premises. The cloud service provider may have access to the keys or the ability to decrypt the data, which may compromise the security and privacy of the data. Moreover, storing the keys on-premises may introduce additional challenges, such as key distribution, synchronization, backup, and recovery3.
* B. Use the cloud service provider's default encryption and key management services: This option is not desirable because it violates the client's requirement of maintaining full control over the encryption keys. Using the cloud service provider's default encryption and key management services means that the client has to trust the cloud service provider to encrypt and decrypt the data on the server-side, using the cloud service provider's own encryption keys and mechanisms. The cloud service provider may have access to the keys or the ability to decrypt the data, which may compromise the security and privacy of the data. Furthermore, the cloud service provider's default encryption and key management services may not meet the regulatory requirements or the security standards of the client4.
* C. Rely on Secure Sockets Layer (SSL) encryption for data at rest: This option is not sufficient because SSL encryption is not designed for data at rest, but for data in transit. SSL encryption is a protocol that encrypts the data as it travels over the internet between the client and the server, using certificates and keys that are exchanged and verified by both parties. SSL encryption can protect the data from being intercepted or modified by unauthorized parties, but it does not protect the data from being accessed or decrypted by the cloud service provider or any third party who has access to the server. Moreover, SSL encryption does not provide the client with any control over the encryption keys or the security of the data.
References:
1: Client-side encryption - Wikipedia
2: What is Client-Side Encryption? | Definition, Benefits & Best Practices | Kaspersky
3: Cloud Encryption Key Management: What You Need to Know | Thales
4: Cloud Encryption: How It Works and How to Use It | Comparitech
5: What is SSL Encryption and How Does it Work? | Norton

The host command in Linux is used for DNS lookup operations. The switch -t specifies the type of DNS record you are querying.
host -t a domain.com queries for A (Address) records, which return the IP address associated with a domain.
host -t ns queries for name servers (NS records).
host -t soa queries for the Start of Authority (SOA) record.
host -t AXFR attempts a zone transfer (not a standard resolution method and typically blocked).
Hence, option A correctly resolves a domain name to its IP address.
Reference:
CEH v13 eCourseware - Module 02: Footprinting and Reconnaissance # DNS Enumeration Tools CEH v13 Study Guide - Chapter: Reconnaissance Techniques # "host Command Usage for DNS Information Gathering"

After the attacker completes preparations, subsequent step is an effort to realize an edge within the target's environment. a particularly common entry tactic is that the use of spearphishing emails containing an internet link or attachment. Email links usually cause sites where the target's browser and related software are subjected to varied exploit techniques or where the APT actors plan to social engineer information from the victim which will be used later. If a successful exploit takes place, it installs an initial malware payload on the victim's computer. Figure 2 illustrates an example of a spearphishing email that contains an attachment.
Attachments are usually executable malware, a zipper or other archive containing malware, or a malicious Office or Adobe PDF (Portable Document Format) document that exploits vulnerabilities within the victim's applications to ultimately execute malware on the victim's computer. Once the user has opened a malicious file using vulnerable software, malware is executing on the target system. These phishing emails are often very convincing and difficult to differentiate from legitimate email messages. Tactics to extend their believability include modifying legitimate documents from or associated with the organization. Documents are sometimes stolen from the organization or their collaborators during previous exploitation operations.
Actors modify the documents by adding exploits and malicious code then send them to the victims. Phishing emails are commonly sent through previously compromised email servers, email accounts at organizations associated with the target or public email services. Emails also can be sent through mail relays with modified email headers to form the messages appear to possess originated from legitimate sources. Exploitation of vulnerabilities on public-facing servers is another favorite technique of some APT groups. Though this will be accomplished using exploits for known vulnerabilities, 0-days are often developed or purchased to be used in intrusions as required .

Gaining an edge within the target environment is that the primary goal of the initial intrusion. Once a system is exploited, the attacker usually places malware on the compromised system and uses it as a jump point or proxy for further actions. Malware placed during the initial intrusion phase is usually an easy downloader, basic Remote Access Trojan or an easy shell. Figure 3 illustrates a newly infected system initiating an outbound connection to notify the APT actor that the initial intrusion attempt was successful which it's able to accept commands.