🔐 System Vulnerability Checklist

A security assessment and network hardening exercise conducted against a vulnerable Linux target machine. The project focuses on identifying critical vulnerabilities, assessing their impact, and implementing firewall-based mitigation using IPTables.

📌 Project Overview

Project Title: Penetration Testing & Network Security Hardening
Role: Cybersecurity Analyst (DecodeLabs Internship)
Target IP: 192.168.56.128
Date: 01 August 2026

This project demonstrates a complete penetration testing workflow, including:

• Host discovery
• Service enumeration
• Vulnerability assessment
• Security analysis
• Firewall hardening
• Post-remediation verification

🎯 Objectives

• Identify exposed network services.
• Detect known vulnerabilities.
• Analyze the security impact of each finding.
• Reduce the attack surface using IPTables.
• Verify the effectiveness of implemented security controls.

🛠️ Tools Used

• Nmap
• IPTables
• Ping
• Kali Linux
• Metasploitable 2 (Target Machine)

Phase 1 – Target Discovery

Network Reachability

The target host was first verified to ensure it was online.

Command

ping -c 4 192.168.56.128

Result

• 100% packet delivery
• Average latency: 1.74 ms

This confirmed that the target machine was reachable.

Service Enumeration

Command

nmap -sV -p 21,22,23,80 192.168.56.128

Open Services

Phase 2 – Vulnerability Assessment

1. Anonymous FTP Login

Command

nmap --script ftp-anon -p 21 192.168.56.128

Risk Level

High

Finding

Anonymous FTP login was enabled.

Security Impact

• Unauthorized file access
• Possible data leakage
• Potential unauthorized uploads

2. vsFTPd 2.3.4 Backdoor

Command

nmap -sV --script vuln -p 21,23,139,445 192.168.56.128

CVE

CVE-2011-2523

Risk Level

Critical

Finding

The installed version of vsFTPd 2.3.4 contains a well-known malicious backdoor.

Security Impact

Successful exploitation can result in:

• Remote Code Execution (RCE)
• Root-level access
• Complete system compromise

3. Telnet Service

Risk Level

Medium

Finding

Port 23 was running the Telnet service.

Security Impact

Because Telnet sends data in plaintext:

• Credentials can be intercepted
• Sessions can be monitored
• Vulnerable to Man-in-the-Middle attacks

Phase 3 – Network Hardening

To reduce the attack surface, firewall rules were implemented using IPTables.

Block FTP

sudo iptables -A OUTPUT -d 192.168.56.128 -p tcp --dport 21 -j DROP

Block Telnet

sudo iptables -A OUTPUT -d 192.168.56.128 -p tcp --dport 23 -j DROP

These rules prevent communication with the vulnerable services while preserving the rest of the network connectivity.

Phase 4 – Verification

A follow-up scan was performed to verify that the firewall rules were active.

Command

sudo nmap -Pn -p 21,23 192.168.56.128

Results

PORT   STATE      SERVICE
21/tcp filtered   ftp
23/tcp filtered   telnet

Outcome

Both vulnerable services changed from OPEN to FILTERED, indicating that the firewall successfully blocked network access.

Security Recommendations

• Replace FTP with SFTP.
• Upgrade or remove vulnerable vsFTPd 2.3.4.
• Disable Telnet permanently.
• Use SSH for remote administration.
• Perform periodic vulnerability scans.
• Enable firewall logging and continuous monitoring.

Project Workflow

Target Discovery
        │
        ▼
Port Scanning
        │
        ▼
Service Enumeration
        │
        ▼
Vulnerability Identification
        │
        ▼
Risk Analysis
        │
        ▼
Firewall Hardening (IPTables)
        │
        ▼
Verification Scan
        │
        ▼
Security Recommendations

Key Learning Outcomes

• Network reconnaissance using Nmap
• Service and version enumeration
• Vulnerability identification
• CVE analysis
• Firewall configuration using IPTables
• Verification of implemented security controls
• Security reporting and documentation

Disclaimer

This project was performed in a controlled lab environment for educational purposes only. All testing was conducted on intentionally vulnerable systems with proper authorization.