A very interesting study on early (almost zero-day) detection of malware: http://winnow.oitc.com/AntiVirusPerformance.html Here the performance of prevx has dropped quickly. From position 6-7 to 13 and detection rate from ca. 45% to 35%. And, if you think about it: the result is cumulative, so the performance has actually collapsed. Perhaps there is at the moment something wrong with the implementation of Prevx on Virustotal?