Vulnerability detection is a critical phase in the penetration testing process. It involves identifying security weaknesses in systems, networks, and applications that could be exploited by attackers. This module will cover the fundamental concepts, tools, and techniques used in vulnerability detection.

1. Vulnerability: A flaw or weakness in a system's design, implementation, or operation that can be exploited to violate the system's security policy.
2. Vulnerability Assessment: The process of identifying, quantifying, and prioritizing vulnerabilities in a system.
3. False Positive: A vulnerability that is reported but does not actually exist.
4. False Negative: A vulnerability that exists but is not detected by the assessment tools.

• Software Vulnerabilities: Bugs or flaws in software applications, such as buffer overflows, SQL injection, and cross-site scripting (XSS).
• Network Vulnerabilities: Weaknesses in network configurations, such as open ports, weak encryption, and insecure protocols.
• Configuration Vulnerabilities: Misconfigurations in systems or applications, such as default passwords, unnecessary services, and improper permissions.

Several tools are available for detecting vulnerabilities. Here are some of the most commonly used ones:

Nmap (Network Mapper) is a powerful tool used for network discovery and security auditing. Below is an example of how to use Nmap to detect vulnerabilities.

1. Install Nmap:

   sudo apt-get install nmap
   

2. Basic Scan: Perform a basic scan to detect open ports on a target system.

   nmap -sV target_ip
   

   • -sV: Service/version detection.

3. Vulnerability Scan: Use Nmap scripts to detect vulnerabilities.

   nmap --script vuln target_ip
   

   • --script vuln: Runs a set of scripts that check for vulnerabilities.

• The basic scan (nmap -sV target_ip) will identify open ports and the services running on them, including their versions.
• The vulnerability scan (nmap --script vuln target_ip) uses Nmap's scripting engine to run various scripts that check for known vulnerabilities in the detected services.

1. Objective: Perform a basic Nmap scan to identify open ports and services on a target system.
2. Steps:
   • Install Nmap if not already installed.
   • Run the following command:

     nmap -sV 192.168.1.1
     

   • Analyze the output to identify open ports and services.

1. Command:

   nmap -sV 192.168.1.1
   

2. Expected Output:

   Starting Nmap 7.80 ( https://nmap.org ) at 2023-10-05 12:00 UTC
   Nmap scan report for 192.168.1.1
   Host is up (0.0010s latency).
   Not shown: 996 closed ports
   PORT    STATE SERVICE VERSION
   22/tcp  open  ssh     OpenSSH 7.6p1 Ubuntu 4ubuntu0.3 (Ubuntu Linux; protocol 2.0)
   80/tcp  open  http    Apache httpd 2.4.29 ((Ubuntu))
   443/tcp open  ssl/https
   3306/tcp open  mysql   MySQL 5.7.29-0ubuntu0.18.04.1
   

1. Objective: Use Nmap to perform a vulnerability scan on a target system.
2. Steps:
   • Run the following command:

     nmap --script vuln 192.168.1.1
     

   • Review the output to identify any detected vulnerabilities.

1. Command:

   nmap --script vuln 192.168.1.1
   

2. Expected Output:

   Starting Nmap 7.80 ( https://nmap.org ) at 2023-10-05 12:10 UTC
   Nmap scan report for 192.168.1.1
   Host is up (0.0010s latency).
   Not shown: 996 closed ports
   PORT    STATE SERVICE
   22/tcp  open  ssh
   | sshv1: 
   |   VULNERABLE:
   |   SSH Server CBC Mode Ciphers Enabled
   |     Security risk: LOW
   |     Description:
   |       The SSH server is configured to support Cipher Block Chaining (CBC) encryption. This may allow an attacker to recover plaintext messages from the ciphertext.
   |     References:
   |       https://nmap.org/nsedoc/scripts/sshv1.html
   |     Solution:
   |       Disable CBC mode cipher encryption, and enable CTR or GCM cipher mode encryption.
   |   
   80/tcp  open  http
   | http-vuln-cve2017-5638: 
   |   VULNERABLE:
   |   Apache Struts 2 Remote Code Execution Vulnerability
   |     State: VULNERABLE (Exploitable)
   |     IDs:  CVE:CVE-2017-5638
   |     Risk factor: High
   |     Description:
   |       Apache Struts 2.3.5 - 2.3.31 and 2.5.0 - 2.5.10.1 are vulnerable to a remote code execution vulnerability.
   |     References:
   |       https://nmap.org/nsedoc/scripts/http-vuln-cve2017-5638.html
   |     Solution:
   |       Upgrade to Apache Struts version 2.3.32 or 2.5.10.2 or later.
   |   
   

• False Positives: Always verify vulnerabilities manually to avoid false positives.
• Regular Updates: Keep your vulnerability detection tools updated to ensure they can detect the latest vulnerabilities.
• Comprehensive Scanning: Use multiple tools and techniques to ensure comprehensive vulnerability detection.

In this section, we covered the basics of vulnerability detection, including key concepts, types of vulnerabilities, and commonly used tools. We also provided practical examples and exercises to help you understand how to use Nmap for vulnerability detection. In the next module, we will delve into the exploitation of vulnerabilities, where you will learn how to exploit the weaknesses identified during the vulnerability detection phase.