In one embodiment, an apparatus captures a memory dump of a device in a sandbox environment executing a malware sample. The apparatus identifies a cryptographic key based on a particular data structure in the captured memory dump. The apparatus uses the identified cryptographic key to decrypt encrypted traffic sent by the device. The apparatus labels at least a portion of the decrypted traffic sent by the device as benign. The apparatus trains a machine learning-based traffic classifier based on the at least a portion of the decrypted traffic sent by the device and labeled as benign.