The present invention relates to the security of general purpose computing devices, such as laptop or desktop PCs, and more specifically to the detection of malicious software (malware) on a general purpose computing device. A challenge in detecting malicious software is that files are typically scanned for the presence of malicious intent only once (and subsequent rescanning is typically performed in a simplistic manner). Existing methods in the art do not address how to most effectively rescan collections of files in a way that tries to optimize performance and efficacy. Accordingly we present novel methods, components, and systems for intelligently rescanning file collections and thereby enabling retroactive detection of malicious software and also retroactive identification of clean software. These methods may also be useful if additional information is now available regarding a file that might be useful to an end-user or an administrator, even though the file's core disposition might not have changed. More specifically, we describe methods, components, and systems that perform data analytics to intelligently rescan file collections for the purpose of retroactively identifying malware and retroactively identifying clean files. The disclosed invention provides a significant improvement with regard to efficacy and performance compared to previous approaches.