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An OpenVAS vs. Nessus comparison is a battle between two top leaders in the vulnerability scanning market. Each tool has its strengths and weaknesses, but deciding between them will likely come down to your specific use case. Nessus is best for companies that want more of an off-the-shelf vulnerability scanning solution, while the open source OpenVAS is best for organizations that want more customization and integrations.
In this guide, I’ll show you where each tool excels and help you understand the key factors you’ll need to know to decide between these two top vulnerability scanners.
- Nessus: Best for Enterprises and Large Organizations
- OpenVAS: Best for DIY Security Professionals and Smaller Security Teams
Featured Partners: Vulnerability Management Software
Table of Contents
OpenVAS Vs. Nessus At A Glance
Open Vulnerability Assessment System (OpenVAS) and Nessus both function in a similar fashion. After discovering points of weakness, the scanners compare them against a database of known vulnerabilities, identify and rank the discovered security gaps (usually in a summarized report) by severity or risk score, and offer advice or actions to take toward remediation.
| OpenVAS | Nessus | |
|---|---|---|
| Price | ✘ | |
| Platform | ✘ | |
| Ease of Use | ✘ | |
| Functionality | ✘ | |
| Product Updates | ✘ |
Vulnerability scanners comprise a diverse and divergent set of solutions, from tools for software penetration testing (pentesting) to suites that identify and classify IT infrastructure weak points, quantify related cyber risks, and prescribe mitigation strategies and activities to close the discovered security gaps.
Both OpenVAS and Nessus fall into that second category: tools that discover weak points in networked environments like firewalls, applications, and services before cyber attackers seize the opportunity to compromise exposed IT assets. By systematically probing for weaknesses and security flaws, these vulnerability scanners can identify, classify, and enumerate exploitable targets like open ports, services, software versions, and more to help security professionals correct them in an ongoing, timely manner.
How OpenVAS Works
Greenbone’s OpenVAS is available in installable binary and source code form, as a cloud service, as well as a paid-for enterprise version. The solution consists of a myriad of built-in testing modules behind a user-friendly web interface.
It uses a client-server architecture consisting of two main components: the OpenVAS Scanner and the OpenVAS Manager. The OpenVAS Scanner performs the actual vulnerability scanning tasks. OpenVAS Manager orchestrates and manages the scanning process, including scheduling scans, collecting results, and generating reports.
When a vulnerability scan is initiated, OpenVAS Manager communicates with the OpenVAS Scanner to execute the scan according to configured parameters. The scanner systematically probes the target systems or networks, identifying potential vulnerabilities by actively testing for known security issues.
Scanning Techniques
To accomplish this, it employs a variety of techniques—network scanning, service enumeration, and vulnerability checks—to comprehensively assess the security posture of the target environment. As the scan progresses, the OpenVAS Scanner collects data on discovered vulnerabilities and sends this information back to the OpenVAS Manager for analysis and reporting.
Finally, the OpenVAS Manager aggregates the results, prioritizes vulnerabilities based on severity and potential impact, and generates detailed reports that provide actionable insights for remediation efforts, empowering organizations to proactively manage and mitigate security risks.
How Nessus Works
Though once available as a free, open source download, the no-cost version of Nessus is primarily available these days as Tenable Nessus Essentials, a scaled down version of the leading vulnerability scanner. Nessus Essentials allows users to scan environments up to 16 IP addresses per scanner, max.
Like OpenVAS, Nessus uses a client-server architecture—its central server component, Nessus Server, interfaces with client applications Nessus Manager or Nessus Professional depending on the software version. The scanning process starts with the user configuring a scan through the client interface, specifying the target systems or networks, scan parameters, and desired scan type—for example, vulnerability assessment or compliance auditing.
Once initiated, the Nessus Server orchestrates the scanning process, sending instructions to multiple scanning engines distributed across the network to execute the scan concurrently.
Scanning Techniques
During the scanning process, Nessus employs a variety of techniques to identify vulnerabilities, including network scanning, port scanning, service enumeration, and vulnerability checks based on extensive plugins. These plugins contain checks for thousands of known vulnerabilities across diverse platforms and applications.
As the scan progresses, Nessus collects detailed information about discovered vulnerabilities, prioritizing them based on severity and potential impact. Upon completing the scan, Nessus generates comprehensive reports that provide actionable insights into the security posture of the scanned environment, enabling organizations to proactively address weaknesses and mitigate security risks effectively.
OpenVAS Vs. Nessus: Portfolio
While both solutions gained their popularity in open source form, their maintainers are decidedly commercial in nature. Greenbone Networks AG, the developer of the full-featured OpenVAS vulnerability scanner, is a leading German security vendor with a long history in vulnerability analysis solutions for enterprises.
Nessus is maintained by leading cybersecurity enterprise solution provider Tenable, a firm that boasts a customer base consisting of 60 percent of the Fortune 500, 40 percent of the Global 2000, and most of the world’s largest government agencies. Suffice to say, both OpenVAS and Nessus have a sizable footprint in the vulnerability scanner arena.
OpenVAS Vs. Nessus: Partners
In terms of partner coverage, both OpenVAS and Nessus benefit from longstanding, dominant positions in the vulnerability scanning space.
As an open source offering, OpenVAS has made its way into many partner offerings, including ArcSight by OpenText and Acunetix, to name just a few. As the world’s most widely used open source vulnerability management provider, parent company Greenbone also has a sizable partner network and customer base.
Nessus and its parent company Tenable’s partner network is no less impressive. Its vast network of security technology resellers, distributors and ecosystem partners, and managed security service providers (MSSPs) enable Nessus to continue expanding its installation base across the globe.
OpenVAS Vs. Nessus: Use Cases
Nessus is my top choice when it comes to large enterprise environments and vast IT networks that span from on-premises to the cloud. OpenVAS is an ideal solution for small and medium sized organizations looking to implement a battle-tested, yet cost-effective—essentially free—vulnerability scanner for their IT environments.
It’s worth noting that both support authenticated and unauthenticated testing—that is, external and internal vulnerability probing and monitoring.
Unauthenticated Scanning
Unauthenticated scanning helps surface and enumerate perimeter weaknesses such as misconfigured firewalls or faulty web servers that are remotely accessible and potentially exploitable.
Authenticated Scanning
In contrast, authenticated scanning requires direct network access via authenticated means, employing protocols and technologies like remote desktop protocol (RDP), virtual private networks (VPNs), virtual network computing (VNC), and secure shell (SSH). Direct access scanning allows for deeper, more comprehensive scans due to the level of penetration into the target IT environment, enabling security professionals to emulate attackers looking to exploit application and operating system vulnerabilities on endpoint systems and internal servers.
OpenVAS Vs. Nessus: User Reviews
In assessing user reviews, I analyzed user-submitted feedback from the leading software review sites across the web. Fee beats free in this case—Nessus wins out in the court of public sentiment.
| Review Site | Nessus | OpenVAS |
|---|---|---|
| AlternativeTo | 27 Likes | 22 Likes |
| Capterra | 4.7 out of 5 | 4 out of 5 |
| Gartner | 4.3 out of 5 | 4.5 out of 5 |
| GetApp | 4.7 out of 5 | 4 out of 5 |
| G2 | 4.5 out of 5 | 4.4 out of 5 |
| TrustRadius | 7.8 out of 10 | 8.7 out of 10 |
User review scores.
OpenVAS Vs. Nessus: Pricing
From a pricing perspective, OpenVAS vs. Nessus is somewhat of an apples-to-oranges comparison. OpenVAS, as a free vulnerability scanning solution, certainly takes the prize in the eyes of the budget-conscious user. Its source code can be downloaded from GitHub and modified at will, making it an ideal tool for the security professional with development chops. Teams looking to develop a bespoke vulnerability scanning solution without having to start from scratch will also appreciate its no-cost offering.
But enterprises and organizations looking to bolster their security postures on an ongoing basis are less likely to balk at Nessus’ $3,769.50 price tag per one year license. All in all, it comes down to your business’s unique requirements and environments.
OpenVAS Vs. Nessus: Alternatives
The vulnerability scanner market is bigger than two tools, and alternatives to OpenVAS and Nessus range from high-end commercial offerings like Rapid7 Nexpose and SonarSource to lower cost options like Burp Suite and MetaSploit. Seasoned security professionals may even opt to use free penetration testing suites like Kali Linux, which require substantial technical expertise but allow for virtually unlimited power under-the-hood when it comes to scanning capabilities.
OpenVAS Vs. Nessus: Review Methodology
In my evaluation of OpenVAS vs. Nessus, I took into consideration the following factors:
Price | 25 percent
In terms of pricing, I looked at the initial price tag as well as the overall cost of ownership and management, keeping in mind that open source tools more often carry the hidden cost of required technical expertise and management overhead.
Platform | 25 percent
No software platform is (or should be) an island unto itself; platform considerations include integrations, both existing and potential connectivity, as well as the broader fit of the solution into the vendor’s security product ecosystem/suite.
Ease of Use | 25 percent
Security professionals looking to acquire a competent vulnerability scanner may not necessarily favor a streamlined user interface (UI) and pleasant front-end experience over functionality. That said, firms employing a more skills-diverse security staff may benefit greatly from an easy-to-use vulnerability scanner. I evaluated OpenVAS and Nessus from both these angles.
Functionality | 25 percent
Last but not least, I looked at each solution’s general efficacy—that is, does the vulnerability scanner serve its purpose well in surfacing security gaps and vulnerabilities? Both solutions satisfied this set of criteria favorably.
Bottom Line: OpenVAS Vs. Nessus
Nuances abound when comparing OpenVAS and Nessus’ relative strengths and weaknesses in vulnerability scanning, but the choice likely comes down to use case. While OpenVAS has its strengths as an open source and freely available solution, Nessus shines with its comprehensive feature set and robust scanning capabilities—attributes that may ultimately win the hearts and minds of enterprise security professionals.
Read our guide to vulnerability scanning best practices to learn more about how to put these tools to use in the most effective way.
