13 Best Vulnerability Scanner Tools of 2021

Vulnerability scanning, assessment and management all share a fundamental cybersecurity principle: the bad guys can’t get in if they don’t have a way. To that end, an essential IT security practice is to scan for vulnerabilities and then patch them, typically via a patch management system.

Vulnerability scanning tools can make that process easier by finding and even patching vulnerabilities for you, reducing burden on security staff and operations centers. Vulnerability scanners detect and classify system weaknesses to prioritize fixes and sometimes predict the effectiveness of countermeasures. Scans can be performed by the IT department or via a service provider. Typically, the scan compares the details of the target attack surface to a database of information about known security holes in services and ports, as well as anomalies in packet construction, and paths that may exist to exploitable programs or scripts.

Some scans are done by logging in as an authorized user while others are done externally and attempt to find holes that may be exploitable by those operating outside the network. Vulnerability scanning should not be confused with penetration testing, which is about exploiting vulnerabilities rather than indicating where potential vulnerabilities may lie. Vulnerability management is a broader product that incorporates vulnerability scanning capabilities, and a complementary technology is breach and attack simulation, which allows for continuous automated vulnerability assessment.

Top 13 Vulnerability Scanner Tools

  1. Qualys Vulnerability Management
  2. AT&T Cybersecurity
  3. Tenable Nessus
  4. Alibaba Cloud Managed Security Service
  5. Netsparker
  6. Amazon Inspector
  7. Burp Suite
  8. Acunetix Vulnerability Scanner
  9. Intruder
  10. Metasploit
  11. Nmap
  12. IBM Security QRadar
  13. Rapid7 InsightVM (Nexpose)

Qualys Vulnerability Management

The Qualys Vulnerability Management scanner operates behind the firewall in complex internal networks, can scan cloud environments and can also detect vulnerabilities on geographically distributed networks at the perimeter. In addition, it scans containers and endpoints.

Its intuitive and customizable dashboard provides a unified view of all web apps and assets being monitored. Pricing may be higher than some other services but the breadth of protection it offers is extensive.

AT&T Cybersecurity

The AT&T Cybersecurity Vulnerability Scanning Solution can be delivered either as a managed service or run from within IT. It helps detect security vulnerabilities in systems, web applications and network devices.

The vulnerability scanner is part of a larger tool that also includes SIEM and intrusion detection. Known vulnerability signatures are updated continually as new vulnerabilities are identified by AlienVault Labs and Open Threat Exchange intelligence community.

It is probably best as a managed service for IT departments lacking cybersecurity expertise.

Tenable Nessus

Tenable Nessus is a widely used, open source vulnerability assessment tool. It is probably best for experienced security teams, as its interface can be a little tricky to master at first. It can be used in conjunction with penetration testing tools, providing them with areas to target and potential weaknesses to exploit.

Nessus comes with pre-built policies and templates for auditing and patching a variety of IT and mobile assets, customizable reports and automatic offline vulnerability assessment.

Alibaba Cloud Managed Security Service

Alibaba offers a SaaS-based managed service for port inspection, scans for web and system vulnerability, and a vulnerability review to eliminate false positives. The service uses machine learning to detect web vulnerabilities and backdoors, as well as illicit content and website defacement to prevent reputation damage.

Alibaba makes the process easy by performing unlimited scans without any installation, updates or maintenance required. It is focused on the cloud and is probably best for non-U.S. businesses in light of ongoing trade hostilities between the U.S. and China.


Netsparker is very good at what it does – the scanning of websites. But it is not designed to do anything else and so lacks the range of many other products. One plus is its ease of use. Its automated web application security scanning capabilities can also be integrated with third-party tools.

Operators don’t need to be knowledgeable in source code. It’s a good choice for SMBs rather than large enterprises.

Amazon Inspector

If you are an AWS shop, then Amazon Inspector is the automated security assessment service for you. It scans all applications deployed on AWS and can be extended to Amazon EC2 instances, too.

After vulnerability scans and assessments, it provides a detailed list of potential vulnerabilities that are prioritized according to the level of risk. It can also identify a lack of best security practices in applications both while running and before they’re deployed.

Amazon Inspector can’t scan Azure, Google Cloud or on-premises data centers and server rooms. Thus, it’s only recommended for those enterprises and SMBs running mainly on the Amazon cloud.

Burp Suite

Burp Suite is a web vulnerability scanner used in a great many organizations. Although there is a free version available, it is limited in functionality, with no automation capabilities. Those wishing for the complete package for enterprise-wide scalability and automation should be prepared to pay well. Security professionals needing only a good automated vulnerability scanner for testing of code can make do with the Professional version, which is cheaper.

Burp includes a power crawl engine that can crawl web apps and find a wide range of vulnerabilities. It uses an advanced algorithm for scanning dynamic content to better uncover more attack surfaces.

Acunetix Vulnerability Scanner

Acunetix is another tool that only scans web-based applications. But its multi-threaded scanner can crawl across hundreds of thousands of pages rapidly and it also identifies common web server configuration issues. It is particularly good at scanning WordPress. Therefore, those with a heavy WordPress deployment should consider it.

The Acunetix Vulnerability Scanner also includes other integration with other helpful tools, such as Jenkins, Jira and GitHub. It also boasts an impressively low false-positive rate.


Intruder is a cloud-based proactive vulnerability scanner that concentrates on perimeter scanning. Any deeper in the enterprise and it needs to be supplemented by other tools. But it is strong at discovering new vulnerabilities. Therefore, it’s a good choice for those looking to harden the perimeter.

It includes more than 10,000 memorable security checks, including WannaCry, Heartbleed and SQL Injection.


Metasploit covers the scanning and testing of vulnerabilities. Backed by a huge open-source database of known exploits, it also provides IT with an analysis of pen testing results so remediation steps can be done efficiently. However, it doesn’t scale up to enterprise level and some new users say it is difficult to use at first.


Nmap is a port scanner that also aids pen testing by flagging the best areas to target in an attack. That is useful for ethical hackers in determining network weaknesses. As it’s open source, it’s free. That makes it handy for those familiar with the open source world, but it may be a challenge for someone new to such applications. Although it runs on all major OSes, Linux users will find it more familiar.

IBM Security QRadar

IBM Security is a world-leading cybersecurity provider and QRadar lives up to the vendor’s reputation. After scanning a network and correlating the information with network topology and connection data, it manages risk using a policy engine with automated compliance checks.

Its advanced analytics are a powerful tool for preventing security breaches, prioritizing and performing remediation and maintaining regulatory compliance. It also includes an intuitive dashboard that consolidates all of this information into a single view.

Rapid7 Nexpose

Rapid7 Nexpose is a top-rated open source vulnerability scanning solution. It’s able to automatically scan and assess physical, cloud and virtual infrastructures. The tool provides live and interactive dashboards, solution-based remediation and risk scoring and prioritization.

Nexpose automatically detects and scans all new devices connected to a network to provide real time vulnerability identification. It also offers a lightweight endpoint agent for processing information while consuming minimal bandwidth.

What are vulnerability scanners?

Vulnerability scanners are software that searches for, identifies and assesses network and network resources for known weaknesses. They discover and inventory all network access points and connected devices, then compare the findings from the scans to known vulnerabilities in a database. These tools are also capable of detecting anomalies in packet construction and paths that may exist to exploitable programs or scripts.

Key features of vulnerability scanners

The key features of vulnerability scanning software can be broken down into two primary groups, identification and correlation, as well as evaluation.

Identification and correlation

Vulnerability scanners discover and classify devices, open ports, operating systems and software connected to a network, then correlate this information with the latest known vulnerabilities. They can also detect misconfigurations and a lack of security controls and policies.


After identifying a vulnerability, these tools also evaluate and assess the level of risk for each one. They can also perform root cause analysis to find the source of the issue. This information informs which vulnerabilities to prioritize.

External vs. internal vulnerability scanning

External scans are run from outside the network perimeter to identify vulnerabilities for servers and applications that are accessible directly from the internet. Internal scans, on the other hand, identify vulnerabilities that could allow attackers to move laterally throughout a network.

Authenticated vs non-authenticated scanning

Authenticated scans are performed by authenticated users with legitimate login credentials. These scans are typically more comprehensive than non-authenticated scans. They are able to identify poor configurations, insecure registry entries and malicious code and plug-ins.

Non-authenticated scans do not use any login credentials. This is because they are solely a surface-level scan. They identify backdoors, expired certificates, unpatched software, weak passwords and poor encryption protocols.

Penetration testing vs vulnerability scanning

Penetration testing and vulnerability scanning serve similar purposes but use different methods. Penetration testing is used to actually exploit vulnerabilities. Scanning is used to identify where potential vulnerabilities may exist before penetration testing is carried out.

How to select a vulnerability scanning tool

When looking for a vulnerability scanning tool, there are two things to keep in mind:

  1. Ensure it can define compliance rules based on regulations and standards relevant to your organization.

  2. Opt for a tool with an intuitive dashboard that clearly shows risk scores and reports to help prioritize patching efforts.

  3. And look for one that can scan your most critical systems and defenses.

Drew Robb
Drew Robb has been a full-time professional writer and editor for more than twenty years. He currently works freelance for a number of IT publications, including ServerWatch and CIO Insight. He is also the editor-in-chief of an international engineering magazine.

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