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Security researchers have recently discovered infections of macOS malware named "Calisto," one that was seemingly developed in 2016 and may have been a precursor to the "Proton" macOS trojan that started to circulate in 2017.
Article Link: https://appleinsider.com/articles/18/07/25/infections-of-macos-trojan-calisto-discovered-two-years-after-initial-release