Techniques are provided for retroactively identifying malware programs when new signatures become available that later match network traffic previously obtained from the sandbox environment. An exemplary method comprises obtaining a plurality of packet capture files comprising previously captured network communications of malware programs that previously executed in a sandbox environment, wherein each of the packet capture files are associated with a corresponding malware program that generated the network communications; obtaining signatures indicative of at least one malware program; comparing the signatures to the packet capture files; and retroactively identifying a given malware program as malware if a signature matches a given packet capture file associated with the given malware program. A plurality of malware samples that were previously unidentified are optionally correlated with the given malware program based on a scan of additional packet capture files for the signature that matched the given packet capture file.