The output shown in the Output 3 tab is characteristic of TheHarvester, a tool used for open-source intelligence (OSINT) gathering. It enumerates emails, subdomains, hosts, and other information from public sources like search engines. The command theharvester -d someclouddomain.org -l 200 -b google.com correctly specifies the target domain (-d someclouddomain.org), limits the search to 200 results (-l 200), and uses Google as the data source (-b google.com), all of which align with the details presented in the output.

The scenario states that the local DNS server (192.168.20.66) lacks internet access, forcing the use of the public DNS server at 8.8.8.8.

• The nslookup someclouddomain.org 8.8.8.8 command explicitly queries the correct public server, matching the nslookup output.
• The dig @8.8.8.8 ... command is the only dig option that correctly directs the query to the functional public DNS server. The other dig options would fail as they either query the offline local server or the default server (which is the offline local server).

These answers are found by analyzing the whois information in the Output 1 tab.

• Hosting: The whois query for the IP address 245.62.183.203 (an IP for the domain from Output 2) shows the owning organization is "Amazon.com, Inc.", indicating it's hosted on their infrastructure (e.g., AWS).
• Registrar: The whois query for the domain someclouddomain.org explicitly lists the "Registrar: LocalComputerPro's, Inc."
• Registration Date: The same domain whois report shows the "Creation Date: 1993-09-22T04:00:38Z".

Gondaliya, A., & P. S., J. (2022). Information Gathering for Penetration Testing Using Open Source Intelligence. In Advances in Intelligent Systems and Computing (pp. 57-67). Springer, Singapore. This paper discusses various OSINT tools, including TheHarvester, and their command structures for enumerating subdomains and email addresses (p. 61).

Mockapetris, P. (1987). RFC 1035: Domain Names - Implementation and Specification. Internet Engineering Task Force (IETF). This document is the foundational standard for the Domain Name System (DNS), outlining the query types and record structures that tools like dig and nslookup use to retrieve information. Section 4.1 describes query message formats. https://doi.org/10.17487/RFC1035

Daigle, L. (2004). RFC 3912: WHOIS Protocol Specification. Internet Engineering Task Force (IETF). This document specifies the WHOIS protocol used to query databases for information about domain names and IP address spaces, such as registrar, creation date, and contact information. Section 4 details the simple query/response nature of the protocol. https://doi.org/10.17487/RFC3912

Albitz, P., & Liu, C. (2006). DNS and BIND (5th ed.). O'Reilly Media. Chapter 12 provides a comprehensive guide to DNS diagnostics tools, including detailed usage and command-line options for nslookup and dig, such as specifying a target name server for a query (pp. 268-271).

For Part 1, the command is derived directly from the scan output. The presence of SERVICE VERSION requires the -sV switch for version detection. The detailed operating system information (Running: Linux 2.4.X) requires the -O switch for OS detection. The summary line "Not shown: 96 closed ports" combined with the 4 visible open ports confirms that exactly 100 ports were scanned, corresponding to the --top-ports=100 option. The scan log indicates a single host was targeted.

For Part 2, the open TCP ports 139 (netbios-ssn) and 445 (microsoft-ds) indicate active SMB services. These services are historically susceptible to information gathering and misconfiguration exploits. A null session enumeration is a primary technique for anonymously querying these services to gather intelligence like usernames and share names. Following enumeration, testing for weak SMB file permissions on any accessible shares is a standard and critical step for a penetration tester.

Lyon, G. (2024). Nmap Reference Guide. Nmap Project. Retrieved from https://nmap.org/book/man.html

Section: "Version Detection": Describes the -sV option to determine the service and version information of listening ports.

Section: "OS Detection": Describes the -O option to enable remote operating system detection using TCP/IP stack fingerprinting.

Section: "Port Scanning Options": Explains the --top-ports option, which scans the specified number of most common ports from the nmap-services file.

Scarfone, K., Souppaya, M., Cody, A., & Orebaugh, A. (2008). NIST Special Publication 800-115: Technical Guide to Information Security Testing and Assessment. National Institute of Standards and Technology. https://doi.org/10.6028/NIST.SP.800-115

Section 4.3.2, "Network Port and Service Identification": Details the use of port scanners like Nmap to identify active services that may present potential security vulnerabilities.

Section 5.4.1, "Vulnerability Validation Activities": Discusses the process of validating potential vulnerabilities found during discovery, which includes testing for issues like default passwords, weak configurations, and anonymous access (such as NetBIOS null sessions).

Microsoft. (2023, September 21). Secure SMB traffic in Windows Server. Microsoft Learn. Retrieved from https://learn.microsoft.com/en-us/windows-server/storage/file-server/smb-secure-traffic

This document provides official vendor guidance on securing SMB, which is predicated on mitigating the risks posed by attackers, such as eavesdropping and unauthorized access to file shares—the very risks tested for by checking for null sessions and weak permissions.

 The Nmap scan results reveal that the application server (App01.example.com) has its HTTP (port 80) and HTTPS (port 443) ports open to the internet. The network architecture intends for all traffic to be filtered through the CDN/WAF. However, because the application server is directly accessible, an attacker can send requests to it without going through the WAF, effectively bypassing its security protections. This is a common misconfiguration where the origin server is not properly firewalled to accept connections only from the CDN/WAF's IP addresses.

The two most effective preventative measures address the vulnerability at different layers.

1. Network Layer: Restricting communication at the network level is the primary solution. This involves configuring firewall rules or network access control lists (ACLs) on the application server to only accept incoming traffic from the specific IP address ranges of the CDN/WAF. This ensures no other entity on the internet can connect directly.
2. Application Layer: Requiring a custom authentication header adds a second layer of defense. The CDN/WAF is configured to add a secret, custom HTTP header to all requests it forwards to the application server. The application server is then configured to reject any request that does not contain this specific header and value, preventing direct access.

Microsoft Azure Documentation. (2023). Restrict access to a specific Azure region. In Azure Front Door. Microsoft explicitly recommends using IP ACLing for backends to ensure traffic is routed exclusively through the Front Door service. "You can configure your backend to only accept traffic from Azure Front Door's backend IP address range and Azure's infrastructure services. ... This configuration ensures that your backend is only reachable through Azure Front Door."

Amazon Web Services (AWS) Documentation. (2024). Restricting access to an Amazon S3 origin. In Amazon CloudFront Developer Guide. AWS details two methods for securing an origin: using origin access control (OAC) and adding custom headers. The guide states, "You can require that users access your content through CloudFront URLs, not by using Amazon S3 URLs. ... Another way to restrict access to content at an origin is to add custom headers to the requests that CloudFront sends to your origin." (Section: Using custom headers to restrict access).

Chell, S., et al. (2020). The Web Application Hacker's Handbook: Finding and Exploiting Security Flaws (2nd ed.). Wiley. While the book itself is a commercial source, the principles it describes are foundational in cybersecurity academia. It discusses bypassing frontend proxies and WAFs by identifying the direct IP address of the backend server, a technique that is only possible if the backend server's firewall is misconfigured. The standard remediation is to ensure the backend only accepts connections from the trusted frontend proxy. (Chapter 9: Attacking Application Architecture).

The robots.txt file explicitly lists paths such as /wp-admin and /wp-login.php. These are default paths for a WordPress content management system (CMS). WPScan is a specialized vulnerability scanner designed specifically to enumerate users, plugins, themes, and check for known security weaknesses in WordPress installations. Therefore, it is the most appropriate and precise tool for conducting a more in-depth investigation based on the initial reconnaissance. The other tools are incorrect as Mimikatz is for credential extraction, Brakeman is for Ruby on Rails, and SQLmap is for SQL injection testing.

The robots.txt file is not a security mechanism; it is a public file that provides instructions to web crawlers. Listing sensitive directory paths, such as administrative portals (/admin, /wp-admin), in this file is a significant security misconfiguration. It provides attackers with direct knowledge of where to focus their efforts to find login pages and attempt unauthorized access. Recommending the removal of these entries helps to prevent this information disclosure, a practice aligned with the principle of security through obscurity as a supplementary defense layer.

WordPress Documentation. (2023). Hardening WordPress: Security through Obscurity. WordPress.org Codex. While not a peer-reviewed paper, official vendor documentation is an approved source. It discusses that while obscurity is not a replacement for security, hiding common identifiers can deter automated attacks. The presence of /wp-admin in robots.txt directly contradicts this principle.

Reference: WordPress.org Codex, Section on "Security Through Obscurity".

Enge, E., Spencer, S., & Stricchiola, J. (2015). The Art of SEO: Mastering Search Engine Optimization (3rd ed.). O'Reilly Media.

Reference: Chapter 8, "Technical SEO: Site Architecture & Server-Side Issues," discusses the proper use of robots.txt for managing crawler access, explicitly warning against using it to block access to private areas as a security measure because the file's contents are publicly accessible.

OWASP Foundation. (2021). OWASP Web Security Testing Guide (WSTG), Version 4.2.

Reference: Section "4.2.1 Identify Application Entry Points" (WSTG-INFO-01). The guide details how robots.txt is a primary target during the information gathering phase for discovering hidden or administrative paths. The presence of /admin and /wp-admin are classic examples of sensitive information leakage that this test aims to find.

The solution correctly identifies ten common web application attack vectors and maps them to their specific vulnerability types and most effective remediation strategies.

• Command Injection (whoami, ping) involves executing OS commands and is best mitigated by fundamentally disallowing the application from making shell calls (Preventing external calls).
• SQL Injection (waitfor, union select, convert) is most effectively prevented using parameterized queries (prepared statements), which ensure user input is treated as data, not executable code.
• Cross-Site Scripting (XSS) payloads are remediated by input sanitization, specifically output encoding of characters like <, >, and " to prevent the browser from interpreting them as active content.
• File Inclusion (LFI/RFI) attacks are mitigated by sanitizing path-related characters (/, ..) to prevent directory traversal or inclusion of unauthorized files.
• URL Redirects are mitigated by validating and sanitizing user-supplied URLs to prevent redirection to malicious sites.

Buehrer, G. T., Weide, B. W., & Sivilotti, P. A. G. (2005). Using parse tree validation to prevent SQL injection attacks. Proceedings of the 5th international workshop on Software engineering and middleware, 106–113. (Discusses the principles behind preventing SQL commands from being altered by user input, for which parameterized queries are the standard implementation). DOI: https://doi.org/10.1145/1108473.1108476

Stojanovic, N., Truong, H. L., & Dustdar, S. (2011). On Cross-site Scripting Attacks and Their Prevention in Web Application Development. 2011 IEEE 20th International Workshops on Enabling Technologies: Infrastructure for Collaborative Enterprises, 73-78. (See Section III.B for discussion on input validation and output encoding as primary XSS defenses). DOI: https://doi.org/10.1109/WETICE.2011.33

Vogt, P., & Nentwich, F. (2007). A Practical Approach for the Automated Detection of Command Injection Vulnerabilities. IEEE/IST Workshop on Monitoring, Attack Detection and Mitigation. (Section 2 details the mechanics of command injection attacks, illustrating how user input becomes executable code).

Johns, M. (2006). Attacking and Defending PHP/FI. it - Information Technology, 48(1), 24-31. (Section 3, "File Inclusion," describes the mechanisms of both Local and Remote File Inclusion vulnerabilities). DOI: https://doi.org/10.1524/itit.2006.48.1.24

The reconnaissance phase using nmap reveals that the SSH service on port 22 is open. The enumeration phase with enum4linux identifies lowpriv as a valid username. The selected hydra command correctly targets the open SSH service to perform a dictionary-based brute-force attack against the known user lowpriv. The other options are incorrect because they target services that the nmap scan explicitly lists as closed (telnet, rdp, rpcbind), making them impossible to exploit. This makes the hydra command the only viable option to gain initial access.

This sequence is a classic method for privilege escalation on improperly configured Linux systems. By adding a new user with a User ID (UID) of 0 to the /etc/passwd file, that user gains root-level privileges. This attack's success hinges on the attacker having write permissions to the /etc/passwd file. Such permissions might exist directly on the file or be obtained by exploiting a utility with the SUID (Set User ID) bit enabled, such as cp, which was specifically searched for during reconnaissance (find / -perm -u=s).

A complete remediation addresses both the initial point of compromise and the method of escalation.

1. The initial access was achieved by brute-forcing a weak password on the lowpriv account. Therefore, strengthening the password and implementing a strong password policy is the direct remediation for this vector.
2. The privilege escalation was accomplished by overwriting the /etc/passwd file. The reconnaissance command find / -perm -u=s indicates the attacker was looking for SUID vulnerabilities. An SUID bit on the cp command would allow a low-privilege user to run it with root permissions, enabling the overwrite of a system file. Removing unnecessary SUID bits from system binaries is a critical security hardening practice to prevent this escalation path.

Port Scanning & Brute-Force Attacks: In network security assessments, port scanning identifies potential attack surfaces, while password brute-forcing attempts to exploit weak authentication. These are fundamental steps in network penetration testing methodologies.

Saltzer, J. H., & Schroeder, M. D. (1975). The Protection of Information in Computer Systems. Communications of the ACM, 18(7), 38-40. (This foundational paper discusses design principles, including psychological acceptability, which relates to why users choose weak, easily guessable passwords). https://doi.org/10.1145/361011.361062

SUID-based Privilege Escalation: The SUID permission bit is a feature in UNIX-like systems that allows users to execute a file with the permissions of its owner. If a program owned by root has the SUID bit set, it can be a vector for privilege escalation if it has vulnerabilities that can be exploited to run arbitrary code.

Bishop, M., & Snyder, L. (1993). On the security of setuid programs in a UNIX environment. IEEE Transactions on Software Engineering, 19(11), 1096-1102. (This paper provides a formal analysis of SUID program vulnerabilities). https://doi.org/10.1109/TSE.1993.213349

Linux System Hardening: Securing critical system files like /etc/passwd and /etc/shadow is a cornerstone of Linux security. Best practices dictate that these files should not be writable by non-root users, and executable permissions should be tightly controlled.

Red Hat Enterprise Linux 8 Documentation. (2023). Security hardening, Section 2.10. Verifying user and group settings. Official vendor documentation emphasizes verifying the integrity and permissions of authentication files.

Password Security: The use of dictionary attacks highlights the importance of strong, complex passwords that are resistant to guessing.

Garfinkel, S. L. (2009). History of Passwords. MIT Computer Science and Artificial Intelligence Laboratory. This work provides context on the evolution of password systems and the persistent threat of guessing and dictionary attacks. https://www.simson.net/clips/2009/2009.USENIX.History_of_Passwords.pdf

The Nmap scan results indicate that the target host has several open ports, most notably port 139 (netbios-ssn) and port 445 (microsoft-ds). These ports are associated with the NetBIOS and Server Message Block (SMB) protocols, respectively. On older systems, such as the identified Linux 2.4.x kernel, these services are classic targets for specific attack vectors.

1. Null session enumeration is a reconnaissance technique that leverages an unauthenticated (or "null") session to query the SMB service for system information, including usernames, group memberships, and available shares. The presence of open ports 139 and 445 makes this a primary vector to investigate.
2. Weak SMB file permissions are a common vulnerability where file shares are misconfigured to allow unauthorized read or write access. After identifying the open SMB service, checking for insecure file and directory permissions is a logical next step for an attacker.

The other options are not supported by the scan data, as the corresponding ports for services like FTP (21), WebDAV (80/443), or SNMP (161) are not listed as open.

Microsoft Corporation. (2022). [MS-SMB2]: Server Message Block (SMB) Protocol Versions 2 and 3. Microsoft Docs, Section 3.3.5.2, "Receiving an SMB2 SESSION_SETUP Request." This document details the protocol's handling of session establishment, including anonymous and unauthenticated access attempts which are foundational to null session attacks.

Samba Team. (2021). Samba 4.15 Administration Guide. Official Samba Documentation, Chapter 39, "Security." This guide discusses security considerations for Samba, the Linux implementation of the SMB protocol, including parameters like restrict anonymous which directly relate to preventing null session enumeration.

Lyon, G. F. (2009). Nmap Network Scanning: The Official Nmap Project Guide to Network Discovery and Security Scanning. Insecure.Com LLC. Chapter 8, "Remote Host and Service Information," describes how Nmap identifies services like netbios-ssn and microsoft-ds, which are the basis for selecting subsequent attack vectors.

Zalewski, M. (2005). Silence on the Wire: A Field Guide to Passive Reconnaissance and Indirect Attacks. No Starch Press. Chapter 10, "Service-level reconnaissance," discusses techniques for fingerprinting and enumerating network services, including SMB, as a prelude to identifying vulnerabilities like weak permissions or information leaks.

An analysis of the provided images reveals multiple vulnerabilities; however, the most critical one, and the one for which remediation tools are provided, is the expired SSL/TLS certificate. The certificate shown was only valid until July 19, 2018, which breaks the chain of trust for the website and exposes users to potential man-in-the-middle attacks.

The correct procedure to remediate an expired certificate involves four main steps.

1. First, a new Certificate Signing Request (CSR) must be generated on the web server.
2. This CSR is then submitted to a trusted Certificate Authority (CA) for verification and signing.
3. Once the CA issues the new certificate, it must be installed on the server to replace the expired one.
4. Finally, as a cleanup measure, the old, expired certificate can be removed.

National Institute of Standards and Technology (NIST) Special Publication 800-52 Revision 2, Guidelines for the Selection, Configuration, and Use of Transport Layer Security (TLS) Implementations, Section 3.3.1. This document outlines the process for server certificate validation, which includes checking the certificate's validity period. An expired certificate fails this check and must be replaced. The renewal process follows the standard lifecycle of generating a CSR, obtaining a new certificate from a CA, and installing it.

Microsoft Documentation, "Renew an Internet Information Services (IIS) Web Server Certificate," TechNet Library. This official vendor documentation details the standard workflow for certificate renewal. The process explicitly lists creating a renewal request (CSR), submitting the request to a CA, and installing the received certificate on the server, which directly corresponds to the first three steps of the solution.

RFC 5280, Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile, Section 4.1.2.5. This standard specifies the validity field in an X.509 certificate, which defines the period during which the CA warrants that it will maintain information about the status of the certificate. Operating with a certificate outside this period is a violation of the PKI trust model.

Data Loss Prevention (DLP) systems are designed to inspect common data exfiltration channels like email (SMTP), web (HTTP/S), and file transfers (FTP). DNS tunneling is a covert channel technique that encapsulates data within DNS queries. Since DNS traffic (port 53) is fundamental for network operations and is rarely blocked or deeply inspected by security controls, it provides an effective means of bypassing typical DLP solutions. Encoding the data further obfuscates the payload, making it appear as legitimate, albeit unusual, DNS traffic, thereby increasing the likelihood of evading detection.

B. Modern DLP solutions are specifically designed to monitor and block unauthorized data transfers to external cloud storage services, making this a highly conspicuous and easily detectable method.

C. FTP is an older, often unencrypted protocol that is heavily monitored by network security tools, including DLP. Obfuscation alone is unlikely to bypass protocol-level inspection.

D. Email is a primary vector monitored by DLP systems. Furthermore, hashing is a one-way function that destroys the original data, making it useless for exfiltration purposes.

1. MITRE ATT&CK® Framework. (2023). Technique T1071.004: Application Layer Protocol: DNS. MITRE Corporation. Retrieved from https://attack.mitre.org/techniques/T1071/004/.

Reference Detail: The framework notes

"Because DNS is a fundamental protocol that is rarely blocked

it is a good candidate for exfiltration... Command and control traffic can be tunneled over DNS to avoid raising suspicion." This supports the choice of DNS as a method likely to evade security controls.

2. Al-kasassbeh

M.

& Adda

M. (2017). DNS Data Exfiltration. In 2017 10th International Conference on Security of Information and Networks (SIN) (pp. 1-5). IEEE. DOI: 10.1109/SIN.2017.8255000.

Reference Detail: Section III

"DNS EXFILTRATION

" discusses how data can be encoded into subdomains of DNS queries. The paper highlights that "DNS traffic is usually not monitored by security devices such as firewalls and intrusion detection systems

" which directly relates to its ability to evade systems like DLP.

3. Papadogiannaki

E.

Vasiliadis

G.

& Polychronakis

M. (2021). An In-depth Analysis of the DNS Querying Behavior of Botnets. In Proceedings of the 2021 ACM SIGSAC Conference on Computer and Communications Security (CCS '21) (pp. 2569–2586). Association for Computing Machinery. DOI: 10.1145/3460120.3484548.

Reference Detail: While focused on botnets

this paper's analysis of DNS as a covert channel (Section 2.2) reinforces the concept that its ubiquitous and trusted nature makes it an ideal medium for stealthy data transfer

bypassing conventional network monitoring.

The penetration testing process typically involves an initial automated scan to identify potential vulnerabilities, followed by manual validation. The command snmpwalk is used to query a device using the Simple Network Management Protocol (SNMP). The vulnerability scanner likely flagged the target (192.168.1.23) for using a default, weak community string ("public"). The tester is now using snmpwalk to manually confirm this finding. If the command successfully retrieves a large amount of system information, it validates the scanner's result as a true positive. If it fails, the finding may be a false positive. This validation step is crucial for ensuring the accuracy of the final report.

A. Bypass defensive systems to collect more information.

snmpwalk is a standard network query tool; this command does not inherently include any techniques for bypassing firewalls or intrusion detection systems (IDS).

B. Use an automation tool to perform the attacks.

While snmpwalk can be scripted, its use here is a single, manual command for verification, not part of a larger automated attack framework.

C. Script exploits to gain access to the systems and host.

snmpwalk is an enumeration tool used to gather information. It does not execute exploits or directly grant unauthorized access to the target system.

1. National Institute of Standards and Technology (NIST). (2008). Technical Guide to Information Security Testing and Assessment (NIST Special Publication 800-115).

Section 3.3

"Vulnerability Validation

" Page 3-4: This section details the process following initial discovery. It states

"After identifying potential vulnerabilities

security analysts can use a variety of techniques to validate the vulnerability... This process involves manually verifying the vulnerability to confirm that the vulnerability exists and is not a false positive." The use of snmpwalk is a classic example of this manual verification technique for an SNMP-related finding.

2. Baloch

R. (2015). Ethical Hacking and Penetration Testing Guide. CRC Press.

Chapter 6

"Information Gathering

" Section "SNMP Enumeration

" Page 158: This academic textbook describes using tools like snmpwalk specifically for enumerating information from systems with weak SNMP configurations. The context is clearly information gathering and verification of a potential weakness

which aligns with validating a scanner's findings.

3. Net-SNMP Project. (n.d.). snmpwalk [Manual page].

Description Section: The official documentation describes snmpwalk as an application that "uses SNMP GETNEXT requests to query a network entity for a tree of information." This confirms its purpose as a tool for information retrieval

not exploitation or bypassing defenses

thereby supporting the process of validating a potential vulnerability.