Compare the top vulnerability scanning tools for 2023 including free, open source and SaaS-based vulnerability scanners to help keep your company secure.
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The top vulnerability scanning tools for 2023

James Harrison

What is vulnerability scanning, why do you need it, and how do you choose the right tool for your organisation? Check out our list of the best vulnerability scanners in 2023.  

Cyber threats are outpacing society’s ability to prevent them effectively, posing a significant risk to business, society and the global economy, according to the World Economic Forum. While this might make protecting your data and systems seem daunting, a simple proactive step to safeguard your network and systems is to use a vulnerability scanner. These tools assess and monitor your organization's security readiness, identifying any weaknesses so you can fix issues before the hackers find them.

What is vulnerability scanning?

Vulnerability scanning is a systematic process used to identify and address cybersecurity weaknesses in your IT infrastructure and digital systems. When you know where your flaws and weaknesses are, you can address any issues to prevent breaches and unauthorized access to your systems, helping avoid data loss and business disruption. For an in-depth explanation, read our Ultimate Guide here.

How do vulnerability scanners work?

Vulnerability scanners are built to search, monitor, and assess your systems for known weaknesses. While these tools were originally designed to scan the IPs or host names which users provided, some more advanced scanners can also now discover and inventory network access points and all connected devices. By comparing the scan’s findings to known threats, they give you the insights you need to secure your networks and systems.

At its core, a scanner focuses on finding the flaws that hackers look for to breach your systems. That said, different scanners perform different security tasks. To find the right one for your organization, it’s important to understand your needs before diving in. Check out our choice of the best and most used scanners based on real world analysis...


Open Vulnerability Assessment Scanner (OpenVAS) is our free recommendation. It’s a full-featured tool that provides extensive scanning coverage with the ability to scan for 44,306 vulnerabilities (at the last check).

It’s a robust and comprehensive vulnerability scanning and management solution, particularly if you’re a small business or start-up with few internet-facing systems. However, it’s complex to install and configure, so it’s best suited to more technical experts or you may struggle to get the most from OpenVAS.  

Also, it doesn’t support authenticated web-application scans so you’ll need to go elsewhere if this is important to you.


Intruder gives you the same high level of security enjoyed by banks and government agencies. Trusted by over 2,000 companies worldwide, its speed, versatility, and simplicity are designed to make reporting and compliance as easy as possible. You can automatically synchronize with your cloud environments and get proactive alerts when exposed ports and services change across your estate, helping you secure your evolving IT environment. By interpreting the raw data drawn from the leading scanning engines, Intruder returns intelligent reports that are easy to interpret, prioritize and action. Each vulnerability is prioritized by context for a holistic view of all vulnerabilities, saving time and reducing your attack surface. Try our interactive demo below to see it in action.


Known for its ability to scan authenticated web applications, Detectify has added a second offering of attack surface monitoring, making it a valuable tool to pinpoint exactly where you are most vulnerable. It’ll also help you prioritize and fix network vulnerabilities and anomalies. By prioritizing your attack surface, Detectify can monitor large amounts of digital assets to find misconfigurations and vulnerabilities.


Offering 25+ open-source scanning tools for reconnaissance, vulnerability discovery, and offensive security activities, Pentest-tools is popular with highly technical system administrators. While some users value the larger datasets this tool generates, the higher output can be too noisy for non-technical users and smaller teams.


One of the lesser-known scanners on the list, Probely is still a highly capable platform. Its power lies in how the software prioritizes the most important threats. Probely scans your web applications and APIs, claiming to only report security vulnerabilities that matter. This reduces the risk of false positives in reports, which are generated with simple instructions on how to fix the most pressing vulnerabilities.


Acunetix claims to offer the highest XSS and SQL injection rates to offer incredible reach to protect sensitive data. It uses a blend of dynamic application security testing (DAST) and interactive application security testing (IAST) to detect over 7,000 vulnerabilities. These include hard-to-scan places like password-protected areas and multi-level forms. Acunetix’s high level of automation makes prioritizing high-risk areas easier. The scheduling feature makes it simple to schedule one-time or recurring scans in multiple environments too.

Tenable Nessus

With the ability to scan 65,000 common vulnerabilities and exposures (CVEs), Tenable Nessus is one of the most powerful tools on the market and offers greater coverage than anyone else. For enterprise software, it performed highly in our recent comprehensive analysis. The platform usually gets new checks out faster than other tools, and the software behind it is highly configurable and powerful, which makes it ideal for technical users. That's why we use Tenable’s scanning engine to power our Intruder Pro plan – all the power but without the complexity.


Known for its broad scanning capabilities and flexibility, Qualys can scan multiple systems from a single console, including cloud environments and your internal network. Users can create custom reports that segment and prioritise analytical data. These reports can be scheduled and generated on command for more responsive vulnerability management. While the software is advanced, the user experience is quite complex and more suitable for highly technical users.


Rapid7 is a comprehensive solution for vulnerability management, especially for companies with large IT networks. It’s InsightVM provides valuable reports to established security teams in particular. However, smaller organizations may not have the resources and in-house expertise to maximize findings.

Choosing the right vulnerability scanner for your organization

Looking for a vulnerability scanner that gives you all this and more? Look no further than Intruder for continuous and comprehensive coverage. Effortless attack surface management that ensures you can identify weaknesses in your system before hackers do. Sign up for a free trial to get started.

Release Date
Level of Ideal
Before CVE details are published
Limited public information is available about the vulnerability.

Red teamers, security researchers, detection engineers, threat actors have to actively research type of vulnerability, location in vulnerable software and build an associated exploit.

Tenable release checks for 47.43% of the CVEs they cover in this window, and Greenbone release 32.96%.
Day of CVE publish
Vulnerability information is publicly accessible.

Red teamers, security researchers, detection engineers and threat actors now have access to some of the information they were previously having to hunt themselves, speeding up potential exploit creation.

Tenable release checks for 17.12% of the CVEs they cover in this window, and Greenbone release 17.69%.
First week since CVE publish
Vulnerability information has been publicly available for up to 1 week.

The likelihood that exploitation in the wild is going to be happening is steadily increasing.

Tenable release checks for 10.9% of the CVEs they cover in this window, and Greenbone release 20.69%.
Between 1 week and 1 month since CVE publish
Vulnerability information has been publicly available for up to 1 month, and some very clever people have had time to craft an exploit.

We’re starting to lose some of the benefit of rapid, automated vulnerability detection.

Tenable release checks for 9.58% of the CVEs they cover in this window, and Greenbone release 12.43%.
After 1 month since CVE publish
Information has been publicly available for more than 31 days.

Any detection released a month after the details are publicly available is decreasing in value for me.

Tenable release checks for 14.97% of the CVEs they cover over a month after the CVE details have been published, and Greenbone release 16.23%.

With this information in mind, I wanted to check what is the delay for both Tenable and Greenbone to release a detection for their scanners. The following section will focus on vulnerabilities which:

These are the ones where an attacker can point their exploit code at your vulnerable system and gain unauthorised access.

We’ve seen previously that Tenable have remote checks for 643 critical vulnerabilities, and OpenVAS have remote checks for 450 critical vulnerabilities. Tenable release remote checks for critical vulnerabilities within 1 month of the details being made public 58.4% of the time, but Greenbone release their checks within 1 month 76.8% of the time. So, even though OpenVAS has fewer checks for those critical vulnerabilities, you are more likely to get them within 1 month of the details being made public. Let’s break that down further.

In Figure 10 we can see the absolute number of remote checks released on a given day after a CVE for a critical vulnerability has been published. What you can immediately see is that both Tenable and OpenVAS release the majority of their checks on or before the CVE details are made public; Tenable have released checks for 247 CVEs, and OpenVAS have released checks for 144 CVEs. Then since 2010 Tenable have remote released checks for 147 critical CVEs and OpenVAS 79 critical CVEs on the same day as the vulnerability details were published. The number of vulnerabilities then drops off across the first week and drops further after 1 week, as we would hope for in an efficient time-to-release scenario.

Figure 10: Absolute numbers of critical CVEs with a remote check release date from the date a CVE is published

While raw numbers are good, Tenable have a larger number of checks available so it could be unfair to go on raw numbers alone. It’s potentially more important to understand the likelihood that OpenVAS or Tenable will release a check of a vulnerability on any given day after a CVE for a critical vulnerability is released. In Figure 11 we can see that Tenable release 61% their checks on or before the date that a CVE is published, and OpenVAS release a shade under 50% of their checks on or before the day that a CVE is published.

Figure 11: Percentage chance of delay for critical vulnerabilities

So, since 2010 Tenable has more frequently released their checks before or on the same day as the CVE details have been published for critical vulnerabilities. While Tenable is leading at this point, Greenbone’s community feed still gets a considerable percentage of their checks out on or before day 0.

I thought I’d go another step further and try and see if I could identify any trend in each organisations release delay, are they getting better year-on-year or are their releases getting later? In Figure 12 I’ve taken the mean delay for critical vulnerabilities per year and plotted them. The mean as a metric is particularly influenced by outliers in a data set, so I expected some wackiness and limited the mean to only checks released 180 days prior to a CVE being published and 31 days after a CVE being published. These seem to me like reasonable limits, as anything greater than 6 months prior to CVE details being released is potentially a quirk of the check details and anything after a 1-month delay is less important for us.

What can we take away from Figure 12?

Figure 12: Release delay year-on-year (lower is better)

With the larger number of checks, and still being able to release a greater percentage of their remote checks for critical vulnerabilities Tenable could win this category. However, the delay time from 2019 and 2020 going to OpenVAS, and the trend lines being so close, I am going to declare this one a tie. It’s a tie.

The takeaway from this is that both vendors are getting their checks out the majority of the time either before the CVE details are published or on the day the details are published. This is overwhelmingly positive for both scanning solutions. Over time both also appear to be releasing remote checks for critical vulnerabilities more quickly.

Written by

James Harrison

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