I have experience working with the built-in Wazuh vulnerability scanner as well as OpenVAS (Greenbone) in comparation with trial version of Nessus Pro.

Wazuh tends to display an overwhelming number of vulnerabilities, many of which are outdated, some over a decade old with no available patches. These are still presented without filtering options, unlike tools such as Nessus. This lack of filtering makes it difficult to prioritize or manage vulnerabilities effectively. Even when risks are accepted, Wazuh provides no way to exclude them from dashboards, which clutters visibility. Overall, the scan results from Wazuh are significantly less actionable and less accurate compared to Nessus.

OpenVAS offers a filtering option using QoD (Quality of Detection), which helps narrow down results. However, its coverage is significantly less comprehensive than Nessus. In multiple comparisons, Nessus consistently identified around 70% more vulnerabilities. For example, I had several hosts with known critical vulnerabilities that Nessus clearly detected, while OpenVAS either missed them entirely or only flagged vague, generic issues.

My team and I debated for quite a while but ultimately couldn’t choose either option for production use - both had disadvantages that outweighed their benefits and overall value.

Which free vulnerability scanner do you rely on?