76% of desktops and 20% of servers run on Windows, so scanning for vulnerabilities of this huge attack surface is critical for most businesses today.
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Vulnerability scanner for Windows

James Harrison

All software is prone to vulnerabilities and bugs introduced by developers that can cause security weaknesses, and Windows is no exception. Given that 76% of the world’s desktops and 20% of the world’s servers run on Windows, this is a significant attack surface that most companies should be very conscious of.  

Because of its ubiquity, Microsoft has been the number one target for hackers for some time, and they invest a lot in security. But given the extent of their software, they’re still prone to frequent flaws including their latest operating systems Windows 10 and 11.  

In this article we’ll look at some recent high profile Windows vulnerabilities, their potential risks to your business, and how a vulnerability scanner like Intruder makes it easier to uncover them in your systems and devices.

Three high profile Windows vulnerabilities

PrintNightmare (CVE-2021–1675, CVE-2021–34527, and CVE-2021–34481)

When is printing not a nightmare? Admins and IT teams struggle with printers daily. But this particular Windows Print Spooler vulnerability causes a lot of sleepless nights. It’s a bug that means a domain user (once they’ve been authenticated against the remote system) can remotely run code on a Microsoft Windows system as the local SYSTEM user.  

Essentially, this becomes an exploit because it means any “authenticated” user, not just the trusted, permitted admins, can add any ‘Print Driver’ to Windows. Any random user can escalate this privilege to become a domain admin. Then start causing chaos within your networks. We recommend patching any system exposed to the Microsoft Windows Print Spooler, keep running Microsoft security updates, and using a vulnerability scanner.

Proxynotshell (CVE-2022-41040 and CVE-2022-41082)

These two Exchange Server zero-day vulnerabilities were disclosed in September 2022 and chained together in a series of targeted attacks. One is a server-side request forgery flaw, and the other is a remote code execution bug. Although an attacker must be authenticated to exploit them, the low complexity and the potentially damaging impact gave it a ‘severe’ rating. Microsoft released detection and remediation guidance that advises relying on its Defender Antivirus for protection. However, it’s easier to check if you should worry about this vulnerability with a local agent, as an internal scan using a vulnerability scanner for bugs like this is much faster and more accurate.  

HiveNightmare/SeriousSAM (CVE-2021-36934)

SeriousSAM is a local escalation-of-privilege vulnerability affecting some versions of Windows 10. An attacker can exploit this to obtain sensitive system and security data, which could then be used to take full control of affected systems and domains. An attacker with the ability to execute code on a target host could exploit this vulnerability to elevate their privileges to SYSTEM.  

How to use a vulnerability scanner for Windows

Firstly, you need to find all the required patches and updates ‍to fix Windows vulnerabilities as they are announced. You can do it manually, or switch on auto-update and it does it automatically.  

Make sure these updates have actually been applied; some systems may not have been rebooted, or the update may have failed which is where a vulnerability scanner gives you the reassurance you need. If you don't have auto-updates enabled, or if you do and you have a large number of systems, you still need to understand what system needs attention. A vulnerability scanner gives you this visibility.

Bear in mind that when it comes to internal vulnerability scanning, cheap doesn’t mean cheerful. With new Windows vulnerabilities discovered every day, it’s important to use a high-quality vulnerability scanner that offers continuous internal scanning. Intruder’s internal vulnerability scanner is easy to install on all your Windows devices to help identify any known vulnerabilities and emerging threats.  

How to use Intruder’s vulnerability scanner for Windows

Intruder’s internal vulnerability scanner is designed to find weaknesses on systems not exposed directly to the internet. These systems are still accessible to attackers though if an employee is tricked into running malware on their laptop, or visits a link in an email – or if an attacker has managed to gain a foothold on a private network already. So they still need to be hardened against attacks.

As an agent-based scanner, Intruder needs to be installed on every device, but this can be done easily using the installation wizard, or you can do it manually. You can find a detailed installation walkthrough here.  

Intruder is a great choice as a vulnerability scanner for Windows 10 and 11, giving you the flexibility to install it wherever your team demands. It will even scan and uncover unsupported legacy devices running Windows 7 or 8 so you can update them or take them offline. If your team depends on Windows to get things done, Intruder can help you reach your cyber security goals. Try it for free today.  


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.

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Written by

James Harrison

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