An interesting aspect of studying a particular piece of malware is tracing its evolution and observing how the creators gradually add new monetization or entrenchment techniques. Also of interest are developmental prototypes that have had limited distribution or not even occurred in the wild. We recently came across one such sample: a macOS backdoor that we named Calisto.
The malware was uploaded to VirusTotal way back in 2016, most likely the same year it was created. But for two whole years, until May 2018, Calisto remained off the radar of antivirus solutions, with the first detections on VT appearing only recently.