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Nessus is a highly regarded vulnerability assessment tool developed by Tenable, Inc., widely used for identifying, scanning, and assessing vulnerabilities within network environments. It offers comprehensive scanning capabilities, continuous updates with the latest vulnerability checks, and customizable features to suit various security needs and compliance requirements.


Section 1

Installation & Setup

Installation and Setup involves the process of getting Nessus installed and ready for use on your system. This phase is crucial as it lays the groundwork for a successful deployment of Nessus in your cybersecurity infrastructure. Proper installation and configuration are essential to ensure the tool functions correctly and provides accurate vulnerability assessments.

Windows: Begin by downloading the Nessus installer from the official Tenable website. Choose the version appropriate for your operating system. Run the installer as an administrator and follow the on-screen instructions. After installation, start the Nessus service either through the Services management console or by using the command net start nessus.

Linux: Download the Nessus package suitable for your Linux distribution. Use package management commands such as dpkg -i Nessus-<version>.deb for Debian-based systems or rpm -ivh Nessus-<version>.rpm for Red Hat-based systems. After installation, start the Nessus service using systemctl start nessusd.

dpkg -i Nessus-<version>.deb
systemctl start nessusd

After installing Nessus, open your web browser and navigate to https://localhost:8834 to access the Nessus interface. Follow the on-screen instructions to complete the initial setup, which includes creating an administrator account, entering your Nessus license, and downloading the necessary plugins and vulnerability definitions.

Configure scan settings and policies according to your environment’s requirements. This involves setting up scan zones, configuring network ranges, and selecting the types of scans based on the assets you intend to test. Remember to regularly update your scan policies to adapt to new vulnerabilities and changes in your network.

A common issue is Nessus not starting due to port conflicts or missing dependencies. Ensure that port 8834 is not used by another service and that all required dependencies are installed. Check the Nessus logs located in /var/log/nessus/ for specific error messages.

If you encounter problems with plugin updates or license activation, verify your network’s internet access and ensure that your firewall settings do not block Nessus from reaching Tenable’s servers. Re-enter your license information if necessary and manually update plugins as a last resort.

Section 2

Features and Capabilities

Features and Capabilities cover the vast range of functions provided by Nessus to detect and assess vulnerabilities within your network. Understanding these features is key to leveraging Nessus effectively for comprehensive security assessments and vulnerability management.

Nessus provides a wide range of scanning options, from basic vulnerability checks to more advanced configurations for in-depth assessments. Features include credentialed scanning, which allows Nessus to log into systems to check for internal vulnerabilities, and non-credentialed scanning for external assessments.

The tool supports plugin-based architecture, enabling users to customize scans with specific scripts for different applications or environments. Nessus continuously updates its database with the latest vulnerabilities, ensuring your scans reflect current threats.

Nessus is used in various scenarios, from routine network audits to compliance checks and security incident investigations. It’s particularly useful in identifying outdated software, misconfigurations, and other weaknesses that could be exploited by attackers.

The tool can be integrated into continuous integration/continuous deployment (CI/CD) pipelines for automated vulnerability assessments, making it an integral part of DevSecOps practices.

Despite its strengths, Nessus has limitations, such as the inability to perform certain types of advanced testing like social engineering or custom exploit development. It may also generate false positives and negatives, requiring manual verification for accurate results.

Nessus’s performance and accuracy can be affected by network configurations and security controls, such as firewalls and intrusion detection systems, which can block or alter scan traffic.

Section 3

Advanced Usage and Techniques

Advanced Usage and Techniques delve into the more sophisticated features and methodologies that can be employed with Nessus to enhance your cybersecurity efforts. Utilizing these advanced functionalities can significantly improve your organization’s security posture.

Nessus allows for advanced scripting using its Nessus Attack Scripting Language (NASL), enabling users to write custom scripts for specialized scans. This capability is crucial for tailoring assessments to unique environments or specific security requirements.

The tool also offers advanced analysis features, such as host correlation and vulnerability trending, which help in tracking the progress of your security posture over time and identifying recurring issues.

Regularly update Nessus and its plugins to ensure you are detecting the latest vulnerabilities. Schedule scans during off-peak hours to minimize network disruption and ensure accurate results by avoiding scan throttles or blocks.

Review and prioritize scan results based on risk, and apply patches or remediations according to your organization’s security policies. Regularly review and refine scanning policies and practices to adapt to new threats and changes in your network environment.

Nessus can be integrated with other security tools and platforms, such as security information and event management (SIEM) systems, ticketing systems, and orchestration frameworks, to automate response processes and improve incident handling.

Utilize Nessus’s API for custom integrations or to automate scanning and result processing within your security infrastructure, enhancing efficiency and effectiveness in vulnerability management.

Section 4


FAQs address common questions and concerns users may have about Nessus, providing clear and concise answers to assist in understanding and resolving typical issues encountered with the tool.

  • What is the difference between Nessus Professional and Nessus Essentials?
    • Nessus Professional offers full features without limitations, suitable for commercial use, while Nessus Essentials (formerly Nessus Home) is free but limited in functionality and intended for personal, non-commercial use.
  • How often should I update Nessus plugins?
    • Plugins should be updated regularly, ideally daily, to ensure your scans reflect the latest vulnerability checks and threat intelligence.
  • Can Nessus scan through firewalls?
    • Nessus can scan through firewalls, but its effectiveness may be limited by firewall rules and configurations. Proper setup and configuration, such as adjusting firewall rules or using credentialed scans, can help mitigate these limitations.
  • Why are my Nessus scans taking so long?
    • Scan duration can vary based on network size, scan settings, and system performance. Optimizing scan configurations, reducing network scope, and ensuring sufficient resources can help reduce scan times.
  • How do I reduce false positives in Nessus scan results?
    • Reducing false positives involves regularly updating plugins, fine-tuning scan policies, and verifying scan results manually or with additional tools for accuracy.

  • Nessus is a penetration testing tool.
    • While Nessus is a powerful vulnerability assessment tool, it is not a full-fledged penetration testing tool as it does not exploit vulnerabilities.
  • Nessus can replace a comprehensive security program.
    • Nessus is a component of a comprehensive security program but cannot replace the need for a holistic approach to security, including policies, training, and other security measures.
  • Nessus scans are always accurate.
    • Nessus scans are subject to false positives and negatives, and results should be validated for accuracy.
  • Nessus does not need regular updates.
    • Regular updates are crucial for Nessus to accurately assess vulnerabilities based on the latest threat intelligence.
  • Nessus can fully secure a network.
    • Nessus identifies vulnerabilities but does not fix them; remediation based on scan results is essential for improving network security.

Section 5


Commands are essential for efficiently using Nessus, allowing users to manage scans, policies, and configurations directly through the command line. Understanding these commands can enhance your Nessus usage and streamline your vulnerability assessment processes.

Starts the Nessus daemon/service on Linux systems.

systemctl start nessusd




Stops the Nessus daemon/service on Linux systems.

systemctl stop nessusd




Restarts the Nessus service to apply changes or updates.

systemctl restart nessusd





Displays the current status of the Nessus service.

systemctl status nessusd





Rebuilds the Nessus plugin database, useful in case of corruption or issues.

/opt/nessus/sbin/nessuscli fix --reset





The cybersecurity information provided on this site is strictly for educational use. We hold no responsibility for misuse and urge users to apply these skills ethically, on networks or systems where they have explicit authorization – such as a private home lab.