Conduct Vulnerability Assessments with Tenable Nessus: A Step-by-Step Guide

A Step-by-Step Guide to Conducting Vulnerability Assessments with Tenable Nessus

Introduction

In an era where cyber threats are constantly evolving, organizations and individuals must proactively identify and mitigate security vulnerabilities. A Vulnerability Assessment (VA) helps in detecting weaknesses in networks, systems, and applications without exploiting them. This proactive approach ensures that potential security gaps are addressed before they can be exploited by malicious actors.

One of the most widely used tools for vulnerability assessments is Tenable Nessus. Whether you’re an IT administrator, security professional, or home user, Nessus provides an efficient way to scan, detect, and analyze vulnerabilities in your infrastructure. This guide will walk you through installing, configuring, and using Nessus for a comprehensive security assessment.

What is Tenable Nessus?

Tenable Nessus is a powerful vulnerability scanner designed to identify security risks in IT environments. It is available in two versions:

  • Nessus Essentials (Free Version): Suitable for individuals and small environments, allowing up to 16 IP addresses per scan.
  • Nessus Professional (Paid Version): Designed for enterprises, offering advanced scanning features, compliance checks, and enhanced reporting.

Nessus supports both authenticated and unauthenticated scans. Authenticated scans provide deeper insights by logging into systems using protocols like SSH, SMB, and SNMP. Nessus also integrates with the Common Vulnerability Scoring System (CVSS) to assign severity ratings to identified vulnerabilities.

Installing and Configuring Nessus

  1. Download and Install Nessus

Visit the official Tenable website (https://www.tenable.com/products/nessus) and download the appropriate version based on your needs. Follow these steps for installation:

  • Register with your email to receive an activation code.
  • Download the Nessus installer for your operating system (https://www.tenable.com/downloads/nessus).
  • Run the installation wizard and follow the on-screen instructions.
  • Install WinPcap (Windows) or necessary dependencies (Linux/Mac).
  1. Initial Setup and Activation
  • Open a browser and navigate to https://localhost:8834.
  • Accept the SSL certificate warning and proceed.
  • Create an account and enter the activation code received via email.
  • Wait for Nessus to download and configure plugins (this may take some time).

Once the setup is complete, you can access the Nessus dashboard and begin scanning.

Conducting a Vulnerability Assessment with Nessus

  1. Setting Up a New Scan
  • From the Nessus web console, click New Scan.
  • Choose a scan template that suits your assessment needs, such as:
    • Host Discovery (Identifies active devices in the network)
    • Basic Network Scan (Detects common vulnerabilities)
    • Advanced Scan (Offers deeper customization)
    • Web Application Scan (Assesses web-based applications)
    • Compliance Scan (Checks regulatory compliance requirements)
  • Enter the scan name, target IP address/domain, and authentication credentials (optional, for a more thorough analysis).
  • Configure scheduling options if you want the scan to run periodically.
  • Click Launch to start the scan.
  1. Using Scan Policies for Custom Scans
  • Navigate to Policies and create a New Policy.
  • Select a base template and customize settings.
  • Save the policy for future use in scheduled or recurring scans.
  1. Understanding Nessus Plugins

Nessus utilizes plugins to analyze vulnerabilities, which contain:

  • Security risk descriptions
  • Exploitability details
  • Remediation recommendations

Tenable continuously updates these plugins to detect emerging threats.

Interpreting Scan Results

After a scan completes, Nessus provides detailed insights into detected vulnerabilities. Key elements of the results include:

  1. Severity Levels
  • Critical: Requires immediate attention as it poses severe risks.
  • High: Exploitable vulnerabilities that should be patched urgently.
  • Medium: Moderate risks that should be addressed soon.
  • Low: Minimal security impact, but should be reviewed.
  • Info: Informational data with no direct security threat.
  1. Graphical and Detailed Reports
  • Nessus provides visual charts summarizing risk levels.
  • Clicking on individual vulnerabilities displays in-depth descriptions, potential impacts, and recommended fixes.

Exporting and Sharing Reports

Organizations and security teams often need to document their security posture. Nessus allows exporting scan results in various formats:

  • PDF: Graphical reports for presentations.
  • HTML: Web-based reports for easy access.
  • CSV: Raw data for further analysis.

Running Nessus via Command Line (Linux)

For advanced users, Nessus can be controlled via the terminal. To start the Nessus service, use:

sudo systemctl start nessusd

Then, access the Nessus web console at https://localhost:8834 and log in.

Conclusion

Tenable Nessus is an industry-leading vulnerability scanner that empowers organizations and individuals to strengthen their cybersecurity posture. Whether using the free Nessus Essentials or the professional-grade Nessus Pro, regular vulnerability assessments help mitigate security risks and enhance overall network protection.

By incorporating Nessus into your cybersecurity strategy, you can proactively identify, analyze, and remediate potential threats before they lead to security incidents.

Start using Nessus today to safeguard your IT environment and stay ahead of emerging cyber threats!