This Microsoft-prevalence-based analysis report is supplementary to AV-Comparatives’ main report, already published, of the September 2015 File-Detection Test. No additional testing has been performed; rather, the existing test result have been re-analysed from a different perspective, to consider what impact the missed samples are likely to have on customers, according to telemetry data of Microsoft.
Microsoft commissioned this supplementary report. This report is a prototype customer-impact report; improved versions might be provided for future File-Detection Test reports. In this report, customer impact is measured according to prevalence. Essentially, some malware samples pose a greater threat to the average user than others, because they are more widespread. An impact heatmap can be found on http://impact.av-comparatives.org
More information can be read also in this Microsoft blog post.