How to Run Your First Nessus Scan and Interpret the Results Nessus, developed by Tenable, is a world-renowned vulnerability scanner used by security professionals to identify weaknesses in network configurations, outdated software, and security gaps. For beginners, Nessus Essentials provides a free, powerful way to scan up to 16 IP addresses, making it perfect for learning.
This guide will walk you through launching your first scan and understanding the results to improve your security posture. Part 1: Setting Up and Running Your First Scan
Before scanning, ensure you have installed and activated Nessus. 1. Create a New Scan Log into your Nessus interface. Click on Scans in the top navigation bar. Click the New Scan button in the upper-right corner. 2. Select a Template
For your first scan, select the Basic Network Scan template. This template provides a comprehensive, general-purpose scan suitable for most scenarios. 3. Configure Scan Settings Fill in the following essential details:
Name: Give your scan a recognizable name (e.g., “Home Network Scan”).
Targets: Enter the IP address, subnet, or hostname you want to scan (e.g., 192.168.1.1 or 192.168.1.0/24).
Note: The scan settings define which ports to scan and which plugins to enable to detect vulnerabilities. 4. Launch the Scan
Click Submit or Launch to start the process. Nessus will begin:
Host Discovery: Identifying which devices are currently active.
Port Scanning: Probing ports to see what services are running.
Vulnerability Detection: Comparing findings against a database of known vulnerabilities. Part 2: Interpreting the Results
Once the scan is complete, click on the scan name to view the report. Understanding the report is more important than running the scan itself. 1. Understand the Severity Colors
Nessus ranks vulnerabilities by risk level, categorized by color:
🔴 Critical: Immediate action required (e.g., unauthenticated remote code execution).
🟠 High: Serious risk, high priority (e.g., outdated software with known exploits).
🟡 Medium: Moderate risk, should be addressed (e.g., weak encryption).
🔵 Low: Low risk, requires review (e.g., information leakage).
⚪ Info: Informational, usually requires no action (e.g., listed open ports). 2. Analyze the “Vulnerabilities” Tab This tab displays the findings broken down by severity.
Plugin Details: Click a vulnerability to see a description, the CVE ID (Common Vulnerabilities and Exposures), and the solution.
Why it Matters: The details explain how a threat actor could exploit this vulnerability. 3. Review the “Remediation” Tab
This is perhaps the most useful tab for practitioners. It prioritizes actions by listing the vulnerabilities that, when fixed, offer the greatest reduction in risk. Part 3: Next Steps (Actionable Vulnerability Management)
Running the scan is only the first step. Vulnerability management is an ongoing process.
Prioritize: Focus on Critical and High vulnerabilities first.
Mitigate: Update software, patch systems, or change configuration settings as recommended by the Nessus report.
Rescan: Run the scan again to verify that the vulnerabilities have been successfully remediated.
By integrating regular Nessus scans into your routine, you can proactively secure your network before threats are exploited. If you’d like to get the most out of your scans, I can:
Show you how to configure authenticated (credentialed) scans for deeper results Explain how to export reports to present to management List the top 3 things to secure on a home network How to Run a Vulnerability Scan with Nessus | Tenable®