From CEH v13 Module 03: Scanning Networks, OS fingerprinting with Nmap (using the -O option) requires privileged access to craft raw packets (especially SYN, ACK, and ICMP). On Unix/Linux systems:
Root privileges are mandatory to perform TCP/IP stack fingerprinting.
If Nmap is run as a normal user, it fails to initiate OS scanning and exits with a message like "QUITTING!".
So, in this case, the scan fails because the shell opened does not have elevated (root) privileges.
Reference:
CEH v13 Module 03 - OS Fingerprinting Techniques using Nmap
Nmap Man Page: https://nmap.org/book/man-os-detection.html

SQL Injection is a type of attack that exploits a vulnerability in a web application that uses a SQL database.
The attacker injects malicious SQL code into the user input, such as a login form, that is then executed by the database server. This can allow the attacker to access, modify, or delete data, or execute commands on the database server.
The 'UNION' SQL keyword is often used in SQL Injection attacks to combine the results of two or more SELECT statements into a single result set. This can allow the attacker to retrieve additional data from other tables or columns that are not intended to be displayed by the application. For example, if the application uses the following query to check the user credentials:
SELECT * FROM users WHERE username = '$username' AND password = '$password' The attacker can inject a 'UNION' statement to append another query, such as:
' OR 1 = 1 UNION SELECT * FROM credit_cards --
This will result in the following query being executed by the database server:
SELECT * FROM users WHERE username = '' OR 1 = 1 UNION SELECT * FROM credit_cards --' AND password = '$password' The first part of the query will always return true, and the second part of the query will return the data from the credit_cards table. The '-' symbol is a comment that will ignore the rest of the query. The attacker can then see the credit card information in the application's response.
However, some web applications implement security measures to prevent SQL Injection attacks, such as filtering special characters in user inputs. Special characters are symbols that have a special meaning in SQL, such as quotes, semicolons, dashes, etc. By filtering or escaping these characters, the application can prevent the attacker from injecting malicious SQL code. For example, if the application replaces single quotes with two single quotes, the previous injection attempt will fail, as the query will become:
SELECT * FROM users WHERE username = '''' OR 1 = 1 UNION SELECT * FROM credit_cards --'' AND password = '$password' This will result in a syntax error, as the query is not valid SQL.
In this challenging environment, if the hacker still intends to exploit this SQL Injection vulnerability, the strategy that he is most likely to employ is to bypass the special character filter by encoding his malicious input. Encoding is a process of transforming data into a different format, such as hexadecimal, base64, URL, etc. By encoding his input, the hacker can avoid the filter and still inject malicious SQL code. For example, if the hacker encodes his input using URL encoding, the previous injection attempt will become:
%27%20OR%201%20%3D%201%20UNION%20SELECT%20*%20FROM%20credit_cards%20--
This will result in the following query being executed by the database server, after the application decodes the input:
SELECT * FROM users WHERE username = '' OR 1 = 1 UNION SELECT * FROM credit_cards --' AND password = '$password' This will succeed in returning the credit card information, as the filter will not detect the special characters in the encoded input.
Therefore, the hacker is most likely to employ the strategy of bypassing the special character filter by encoding his malicious input, which could potentially enable him to successfully inject damaging SQL queries.
References:
SQL Injection | OWASP Foundation
SQL Injection Union Attacks
SQL Injection Bypassing WAF

https://en.wikipedia.org/wiki/Metasploit_Project
The Metasploit Project is a computer security project that provides information about security vulnerabilities and aids in penetration testing and IDS signature development. It is owned by Boston, Massachusetts-based security company Rapid7.
Its best-known sub-project is the open-source Metasploit Framework, a tool for developing and executing exploit code against a remote target machine. Other important sub-projects include the Opcode Database, shellcode archive and related research.
The Metasploit Project includes anti-forensic and evasion tools, some of which are built into the Metasploit Framework. Metasploit is pre-installed in the Kali Linux operating system.
The basic steps for exploiting a system using the Framework include.
1. Optionally checking whether the intended target system is vulnerable to an exploit.
2. Choosing and configuring an exploit (code that enters a target system by taking advantage of one of its bugs; about 900 different exploits for Windows, Unix/Linux and macOS systems are included).
3. Choosing and configuring a payload (code that will be executed on the target system upon successful entry; for instance, a remote shell or a VNC server). Metasploit often recommends a payload that should work.
4. Choosing the encoding technique so that hexadecimal opcodes known as "bad characters" are removed from the payload, these characters will cause the exploit to fail.
5. Executing the exploit.
This modular approach - allowing the combination of any exploit with any payload - is the major advantage of the Framework. It facilitates the tasks of attackers, exploit writers and payload writers.

The technique that the hacker would consider next to obtain useful information about the underlying database is to utilize a blind injection technique that uses time delays or error signatures to extract information. A blind injection technique is a type of SQL injection technique that is used when the web application does not return any detailed error messages or data from the database, but only indicates whether the query was executed successfully or not. A blind injection technique relies on sending specially crafted SQL queries that cause a noticeable change in the behavior or response of the web application, such as a time delay or an error signature, which can then be used to infer information about the database. For example, the hacker could use the following methods12:
* Time-based blind injection: This method involves injecting a SQL query that contains a time delay function, such as SLEEP() or WAITFOR DELAY, which pauses the execution of the query for a specified amount of time. The hacker can then measure the time difference between the normal and the delayed responses, and use it to determine whether the injected query was true or false. By using this method, the hacker can perform a binary search to guess the values of the data in the database, one bit at a time.
* Error-based blind injection: This method involves injecting a SQL query that contains a deliberate error, such as a division by zero, a type mismatch, or an invalid conversion, which causes the database to generate an error message. The hacker can then analyze the error message, which may contain useful information about the database, such as the version, the name, the structure, or the data. By using this method, the hacker can exploit the error handling mechanism of the database to extract information.
The other options are not as suitable as option D for the following reasons:
* A. Use the UNION operator to combine the result sets of two or more SELECT statements: This option is not feasible because it requires the web application to return data from the database, which is not the case in this scenario. The UNION operator is a SQL operator that allows the hacker to append the results of another SELECT statement to the original query, and display them as part of the web page.
This way, the hacker can retrieve data from other tables or columns that are not intended to be shown by the web application. However, this option does not work when the web application does not return any data or error messages from the database, as in this scenario3.
* B. Attempt to compromise the system through OS-level command shell execution: This option is not relevant because it is not a SQL injection technique, but a post-exploitation technique. OS-level command shell execution is a method of gaining access to the underlying operating system of the web server, by injecting a SQL query that contains a system command, such as xp_cmdshell, exec, or shell_exec, which executes the command on the server. This way, the hacker can perform various actions on the server, such as uploading files, downloading files, or running programs. However, this option does not help to obtain information about the database, which is the goal of this scenario4.
* C. Try to insert a string value where a number is expected in the input field: This option is not effective because it is a basic SQL injection technique that is used to detect SQL injection vulnerabilities, not to exploit them. Inserting a string value where a number is expected in the input field is a method of triggering a syntax error in the SQL query, which may reveal the structure or the content of the query in the error message. This way, the hacker can identify the vulnerable parameters and the type of the database. However, this option does not work when the web application does not return any detailed error messages from the database, as in this scenario5.
References:
* 1: Blind SQL Injection - OWASP Foundation
* 2: Blind SQL Injection - an overview | ScienceDirect Topics
* 3: SQL Injection Union Attacks - OWASP Foundation
* 4: OS Command Injection - OWASP Foundation
* 5: SQL Injection - OWASP Foundation

In CEH v13 Module 09: Social Engineering, scareware is defined as a malicious tactic that uses fear, panic, or urgency to trick users into performing harmful actions such as downloading fake software or clicking malicious links.
Common Scareware Example:
A pop-up warns the user: "Your system is infected! Install this antivirus now!" Victim downloads malware disguised as a solution.
Often used to deliver spyware, ransomware, or trojans.
Option Review:
A). Free cruise: Classic example of baiting, not scareware.
B). Account locked: Closer to phishing or credential harvesting.
C). Delivery delay: Another phishing variation.
D). Pop-up about infection: True scareware tactic.
Reference:
Module 09 - Social Engineering Attacks # Scareware Attacks
CEH iLabs: Identifying Fake Security Alerts and Scareware Payloads