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Explain Nessus tool in security testing

Last Updated : 11 Jan, 2024
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Nessus is a widely used vulnerability scanning tool in the field of cyber security and security testing. Nessus is a platform developed by Tenable that scans for security vulnerabilities in devices, applications, operating systems, cloud services, and other network resources. It is a remote security scanning tool, which scans a computer and raises an alert if it discovers any vulnerabilities that malicious hackers could use to gain access to any computer, that you have connected with any network. It does this by running over 1200 checks on a given computer, to see if any of these attacks could be used to break into the computer or otherwise harm it.

History of Nessus

Originally, it was launched as an open-source tool in 1998, but its enterprise edition became a commercial product in 2005. It was developed in 1998 by Renaud Deraison as an open-source project, Nessus gained popularity for vulnerability scanning. It was acquired by Tenable in 2005, and it transitioned to a partially closed-source model, evolving with features like compliance scanning. Tenable introduced “Nessus Essentials” in 2017 and, a cloud platform leveraging Nessus. In 2023, Nessus remains a trusted tool for organizations globally, reflecting its commitment to adaptability and effectiveness in addressing cybersecurity challenges.

Who uses this tool?

If you are an administrator in charge of any computer or a group of computers connected to the internet, it is a great tool to help keep the domains free of the easy vulnerabilities that hackers and viruses, commonly look to exploit. Some of the people who use this tool are security professionals, IT admins, system and security admins, and software developers.

Nessus is used by a diverse range of organizations and professionals across different industries for vulnerability management and security assessments.

  • Enterprise Organizations: Large enterprises use Nessus to conduct regular vulnerability scans on their networks, servers, and applications. This includes industries such as finance, healthcare, manufacturing, and telecommunications.
  • IT Security Teams: In-house IT security teams within organizations use Nessus as a tool to identify and remediate vulnerabilities in their infrastructure. This includes systems administrators, security analysts, and IT managers.
  • Cloud Service Providers: Organizations that provide cloud services and infrastructure use Nessus to assess the security of their cloud environments, ensuring that customer data and applications are protected.
  • Security Consultants and Service Providers: Security consulting firms and managed security service providers leverage Nessus to offer vulnerability assessment services to their clients. This includes performing security audits, risk assessments, and compliance checks.

Why Nessus?

As we know many organizations and individuals use the Nessus tool for vulnerability assessments and for finding security weaknesses. There are multiple features that make a good choice for organizations and individuals.

  • Vulnerability scanning: Nessus scans servers for known vulnerabilities. For example, detecting outdated Software versions that may be suspectable to exploits.
  • Credential-based scanning: Authenticated scans with login credentials provide Nessus deeper access, enhancing the accuracy of vulnerability detection.
  • Web Application scanning: It identifies the vulnerabilities in web applications such as SQL injection or XSS flaws.
  • Malware detection: Nessus identifies the potential malware indicators by analyzing the system files and configuration.

Types of Nessus Scans:

Nessus supports various types of scans to address different aspects of security assessments. Here are some common types of scans in Nessus:

  • Network Scans: It identifies vulnerabilities in network devices, servers and infrastructure. Example: scanning a range of IP addresses to identify open ports, services and potential vulnerabilities on networked devices.
  • Web Application Scans: It focuses on identifying vulnerabilities in web applications and services. Example: examining a website for common web application vulnerabilities such as SQL injection, cross-site scripting (XSS) and security misconfigurations.
  • Credential Scans: It uses provided credentials to perform authenticated scans for a more in-depth assessment. Example: logging into a server using valid credentials to assess the system from an internal perspective, identifying vulnerabilities that may not be visible externally.
  • Patch Management Scans: Nessus searches for vulnerable software fixes and out-of-date versions that could be used by hackers. It assists companies in making sure that their systems have the most recent security fixes installed.
  • Web-based Application Scans: Web applications can be scanned by Nessus for common security flaws like SQL injection, cross-site scripting (XSS) and other vulnerabilities that could compromise the application’s security.
  • Mobile Device Scans: The purpose of this kind of scan is to assess the safety status of mobile devices, such as tablets and smartphones. It looks for setup errors and security holes that hackers aiming for mobile platforms might exploit.

Benefits of Nessus Scans:

Some major benefits are as follows:

  1. Time cost & Efficiency: Automated scanning reduces the manual effort required for routine vulnerability assessments.
  2. Detailed Reporting: Customized reports generated by Nessus assist in communicating secure posture to stakeholders and management.
  3. Cloud security: Nessus extends it’s scanning capabilities to assess the security of a cloud based infrastructure, ensuring a consistent security posture across all environments.
  4. Setting Risk Priorities: Nessus helps organizations prioritize corrective efforts by classifying vulnerabilities according to their severity. This aids in concentrating efforts on solving pressing problems that are most dangerous for the company.
  5. Adaptable Scanning Procedures: Users can design and modify scanning policies in Nessus according to their own needs. This adaptability guarantees that scans comply with the particular security requirements and guidelines of the company.

Limitations of Nessus Scans:

While Nessus is a powerful and widely-used vulnerability scanning tool, it does have some limitations. Here are a few key considerations:

  1. Scanning Interruptions: Some network configurations or security measures may interrupt Nessus scans, leading to incomplete results. Firewalls, network congestion or rate limiting can impact the scanning process.
  2. Credential Management: Authenticated scans, which provide more detailed results, require proper credentials. Managing and securing these credentials can be challenging, particularly in large and dynamic environments.
  3. False Positives and Negatives: Nessus may produce false positives, incorrectly identifying a vulnerability that doesn’t exist or false negatives, missing actual vulnerabilities. Human verification is often required to validate scan results.
  4. No Real-Time Monitoring: Nessus is not designed for real-time monitoring. It is a point-in-time scanner and continuous monitoring capabilities are limited. Other tools may be required for continuous security monitoring.


Nessus serves as a vital tool in security testing, offering early vulnerable detection, time, cost efficiency, risk prioritization and adaptability to evolving threats. Its customization, compliance assurance and integration capabilities contribute to a more secure and resilient IT Environment, ultimately safeguarding organizations the against potential cyber threats.

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