Hack The Box Optimum
HTBRetired Machines

Retired Machine: Optimum Walkthrough

Posted on

Hack The Box (HTB) is a popular platform for cybersecurity enthusiasts and professionals to practice and enhance their penetration testing skills in a legal and safe environment. One of the beginner-friendly machines on HTB is “Optimum,” which provides a great learning experience for novices in the field. Here’s a detailed overview of a walkthrough catered towards novices for the Optimum machine:

Introduction to Optimum Machine:

Optimum is a vulnerable Windows machine that simulates real-world scenarios commonly encountered in cybersecurity assessments. The objective is to gain unauthorized access to the machine and retrieve a flag, demonstrating successful exploitation.

Enumeration:

Enumerating the Optimum machine involves gathering information about its configuration, open ports, running services, and potential entry points for exploitation. Here’s a step-by-step guide for novice users on how to perform enumeration:

Scan for Open Ports:

  • Use a network scanning tool like Nmap to scan the Optimum machine for open ports.
  • Open a terminal window and execute the following command:
    nmap -p- -sV <machine_ip>
    Replace <machine_ip> with the IP address of the Optimum machine.
  • This command performs a comprehensive scan of all ports (-p-) and identifies the services running on each port (-sV).

Identify Running Services:

  • Review the output of the Nmap scan to identify the services running on open ports.
  • Note down the service names and versions, as they may reveal potential vulnerabilities that can be exploited.

Enumerate Web Services:

  • If the Nmap scan reveals open ports associated with web services (e.g., HTTP on port 80 or HTTPS on port 443), perform web enumeration to gather additional information.
  • Use tools like Dirb, Dirbuster, or Gobuster to enumerate directories and files on web servers.
  • Execute the following command to perform directory enumeration with Dirb:
    dirb http://<machine_ip> /usr/share/dirb/wordlists/common.txt
    Replace <machine_ip> with the IP address of the Optimum machine.

Enumerate SMB Shares:

  • If the Nmap scan detects the SMB service (port 445), enumerate SMB shares to identify accessible file shares and resources.
  • Use tools like Enum4linux or smbclient to enumerate SMB shares and gather information about shared files and directories.
  • Execute the following command to enumerate SMB shares with Enum4linux:
    enum4linux <machine_ip>
    Replace <machine_ip> with the IP address of the Optimum machine.

Perform Version Enumeration:

  • Identify services with known vulnerabilities by enumerating their versions.
  • Use tools like Nmap or Netcat to connect to specific ports and retrieve service banners or version information.
  • Execute the following command to retrieve version information for a service using Netcat:
    nc <machine_ip> <port>
    Replace <machine_ip> with the IP address of the Optimum machine and <port> with the port number of the target service.

Analyze Results:

  • Review the results of your enumeration efforts to identify potential entry points for exploitation.
  • Look for outdated software versions, misconfigurations, or default credentials that may indicate security vulnerabilities.

By following these enumeration steps, novice users can gather essential information about the Optimum machine and identify potential vulnerabilities to exploit during penetration testing.

Identifying Vulnerabilities:

Once you’ve identified open ports and services on the Optimum machine, it’s crucial to research known vulnerabilities associated with those services. Here’s a more detailed guide, including specific vulnerabilities and how to exploit them:

HTTP Service (Port 80/443):

  • Research known vulnerabilities associated with the web server software running on ports 80 (HTTP) and 443 (HTTPS). Common vulnerabilities may include:
    • Outdated Software Versions: Check if the web server is running outdated software versions, such as Apache, Nginx, or IIS. Vulnerabilities like Remote Code Execution (RCE), SQL Injection, or Cross-Site Scripting (XSS) may exist in older versions.
    • CMS Vulnerabilities: If the website is powered by a Content Management System (CMS) like WordPress, Joomla, or Drupal, search for vulnerabilities specific to that CMS version. Exploitable vulnerabilities in plugins, themes, or core files are common.
    • File Upload Vulnerabilities: Look for file upload functionalities on the website. Insecure file upload mechanisms can lead to arbitrary code execution if not properly sanitized.
  • Exploit these vulnerabilities using tools like Metasploit, Burp Suite, or manual exploitation techniques. For example, use SQLMap for SQL injection, WPScan for WordPress vulnerabilities, or manual exploitation for file upload vulnerabilities.

SMB Service (Port 445):

  • The SMB service may expose file shares and resources. Common vulnerabilities and misconfigurations to explore include:
    • Null Session: Attempt to establish a null session to enumerate shares and gather information about the system.
    • SMB Signing Disabled: If SMB signing is disabled, it may be possible to perform man-in-the-middle attacks or relay attacks to gain unauthorized access to resources.
    • Default Credentials: Some installations may have default credentials enabled. Research default credentials for common systems and attempt to authenticate.
  • Exploit these vulnerabilities using tools like Enum4linux for enumeration, Impacket for relay attacks, or manual exploitation techniques.

Other Services:

  • Research vulnerabilities associated with any other identified services, such as FTP (Port 21), SSH (Port 22), or database servers (e.g., MySQL on Port 3306).
  • For example, outdated versions of FTP servers may be vulnerable to anonymous login or arbitrary file upload/download. Weak SSH configurations may allow brute force attacks or SSH key-based authentication bypass.
  • Exploit these vulnerabilities using appropriate tools and techniques tailored to the specific service and vulnerability.

By researching known vulnerabilities associated with the identified services on the Optimum machine, you can effectively pinpoint potential entry points for exploitation and proceed with targeted attacks to gain unauthorized access. Always ensure you have appropriate permissions and authorization before attempting any exploitation activities.

Exploitation:

Once you’ve identified vulnerabilities on the Optimum machine, it’s essential to select an appropriate exploit to gain initial access. Here’s a detailed guide on how to proceed:

Identify Vulnerabilities:

  • Review the results of your enumeration and research to identify specific vulnerabilities present on the Optimum machine. This may include outdated software versions, misconfigurations, default credentials, or other known vulnerabilities associated with the services running on the machine.

Select an Exploit:

  • Once you’ve identified vulnerabilities, select an appropriate exploit to gain initial access to the Optimum machine. Consider factors such as the severity of the vulnerability, the ease of exploitation, and the likelihood of success.
  • You can find exploits for known vulnerabilities in various exploit databases, security forums, or integrated within penetration testing frameworks like Metasploit.
  • Choose an exploit that aligns with the identified vulnerabilities. For example, if the machine is running an outdated version of a service like SMB, you may opt for exploits targeting specific vulnerabilities like EternalBlue (MS17-010) or MS08-067.

Prepare the Exploit:

  • If using Metasploit, open the Metasploit framework by running the command msfconsole in your terminal.
  • Search for the desired exploit module using the search command followed by relevant keywords. For example:
    search MS17-010
  • Once you’ve identified the appropriate exploit module, load it using the use command. For example:
    use exploit/windows/smb/ms17_010_eternalblue

Configure the Exploit:

  • Set any required options for the exploit module, such as the target IP address (RHOST) and port number (RPORT). Use the show options command to view and set the required parameters.
  • For example:
    set RHOST <IP_Address>

Execute the Exploit:

  • Once the exploit module is configured, execute the exploit using the exploit command. This will initiate the exploitation process and attempt to gain access to the target machine.
  • Monitor the output for any indications of successful exploitation, such as obtaining a shell or system-level access to the target machine.

Verify Access:

  • After executing the exploit, verify whether you’ve successfully gained initial access to the Optimum machine. This may involve checking for a remote shell, verifying system-level privileges, or confirming the presence of a backdoor or persistence mechanism.

By following these steps, you can select and execute an appropriate exploit to gain initial access to the Optimum machine based on identified vulnerabilities. Remember to exercise caution and ensure you have appropriate authorization before attempting any exploitation activities.

Privilege Escalation:

Once you’ve gained initial access to the Optimum machine, the next step is to escalate privileges to obtain higher-level access. Here’s a detailed guide on how to proceed with privilege escalation:

Identify Weaknesses:

  • Conduct further enumeration and analysis to identify potential weaknesses that could lead to privilege escalation. This may include misconfigured permissions, weak passwords, or vulnerable services running on the Optimum machine.

Exploit Weaknesses:

  • Look for specific vulnerabilities or misconfigurations that can be exploited to escalate privileges. Common techniques include:
    • Exploiting misconfigured file permissions to gain access to sensitive files or directories.
    • Cracking weak passwords for user accounts with elevated privileges.
    • Leveraging vulnerabilities in system services or software to execute arbitrary code with higher privileges.
    • Exploiting weaknesses in scheduled tasks, registry settings, or system configurations to escalate privileges.

Use Privilege Escalation Tools:

  • Utilize tools like Windows Exploit Suggester (WES) to assist in identifying potential privilege escalation vulnerabilities. The Windows Exploit Suggester tool analyzes the system’s configuration and installed software to suggest relevant exploits.
  • Download the Windows Exploit Suggester script and the corresponding database file (2020-06-02-mssb.xls in this example) to your local machine.
  • Run the Windows Exploit Suggester script with the appropriate command-line options, specifying the path to the database file:
    python windows-exploit-suggester.py --database 2020-06-02-mssb.xls
  • Review the output generated by the tool to identify relevant exploits and vulnerabilities that may lead to privilege escalation on the Optimum machine.

Exploit Identified Vulnerabilities:

  • Once potential privilege escalation vulnerabilities are identified, research and select appropriate exploits to exploit them. Ensure that the selected exploits are compatible with the target system’s configuration and software versions.
  • Use penetration testing frameworks like Metasploit or manually execute the exploits to escalate privileges and gain higher-level access on the Optimum machine.

Verify Privilege Escalation:

  • After executing privilege escalation exploits, verify whether you’ve successfully escalated privileges on the Optimum machine. Check for indicators such as obtaining administrative or SYSTEM-level access, accessing sensitive system resources, or gaining persistence on the system.

By following these steps and leveraging privilege escalation techniques, you can elevate your access level on the Optimum machine and achieve deeper penetration into the target system. Remember to conduct privilege escalation activities responsibly and with appropriate authorization to avoid unauthorized access or disruption to systems.

Retrieve the Flag:

After successfully escalating privileges on the Optimum machine, you’ll need to navigate through the system to locate the flag file containing the challenge key. Here are some common locations where flag files may be found:

Desktop Directory:

  • Check the desktop directory of the compromised user account. Flag files are sometimes placed on the desktop for easy access.
   C:\Users\<username>\Desktop\

Documents Directory:

  • Explore the documents directory of the compromised user account. Users often store files, including flag files, in this location.
   C:\Users\<username>\Documents\

Downloads Directory:

  • Look in the downloads directory of the compromised user account. Users may download files, including flag files, from the internet and store them here.
   C:\Users\<username>\Downloads\

AppData Directory:

  • Search the AppData directory, which contains user-specific application data. Flag files may be stored in subdirectories within AppData.
   C:\Users\<username>\AppData\

System Directories:

  • Check system directories accessible to the compromised user account, such as system32 or Program Files. Flag files may be hidden or stored in less obvious locations within these directories.
   C:\Windows\System32\
   C:\Program Files\

Temporary Directories:

  • Investigate temporary directories where temporary files and caches are stored. Flag files may be temporarily stored in these directories during system operations.
   C:\Users\<username>\AppData\Local\Temp\

User Profile Directories:

  • Explore other directories within the user profile, such as Music, Pictures, or Videos. While less common, flag files may be hidden or stored in unconventional locations.
   C:\Users\<username>\Music\
   C:\Users\<username>\Pictures\
   C:\Users\<username>\Videos\

Remember to search thoroughly and examine any suspicious or unusual files you encounter. Once you locate the flag file containing the challenge key, you can retrieve it and proceed with completing the challenge.

Documentation:
Document the steps taken during the walkthrough, including enumeration, exploitation, and privilege escalation. This documentation helps reinforce learning and serves as a reference for future assessments.

Post-Exploitation Cleanup:
After completing the challenge, ensure to clean up any traces or artifacts left on the Optimum machine. Remove any backdoors, delete log files, and restore system configurations to their original state.

Learning and Improvement:
Reflect on the experience gained from the Optimum walkthrough. Identify areas for improvement, explore alternative exploitation techniques, and continue learning about cybersecurity concepts and methodologies.

By following this walkthrough, novices can gain practical experience in penetration testing and develop essential skills for assessing and securing computer systems. Remember to approach challenges on Hack The Box ethically and responsibly, adhering to the platform’s terms of service and guidelines.