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Ransomware continues to be one of the most prevalent and impactful threats affecting organizations, with attackers constantly evolving their techniques and expanding their tradecraft to cast a wider net of potential targets. This is evident in the range of industries, systems, and platforms affected by ransomware attacks. Understanding how ransomware works across these systems and platforms is critical in protecting today’s hybrid device and work environments.
This blog provides details from our analysis of known ransomware families affecting macOS devices. As in other platforms, the initial vector of Mac ransomware typically relies on user-assisted methods like downloading and running fake or trojanized applications. It can, however, also arrive as a second-stage payload dropped or downloaded by other malware or part of a supply chain attack. Once running on a device, ransomware attacks usually comprise gaining access, execution, encrypting target users’ files, and notifying the target with a ransom message.
To perform these actions, malware creators abuse legitimate functionalities and devise various techniques to exploit vulnerabilities, evade defenses, or coerce users to infect their devices. We describe these techniques in detail below, based on our analysis of four Mac ransomware families: KeRanger, FileCoder, MacRansom, and EvilQuest. In particular, we take a deeper look at EvilQuest and one of its variants that had its ransomware component removed but was further improved with additional techniques and anti-analysis logic.
While these malware families are old, they exemplify the range of capabilities and malicious behavior possible on the platform. Building durable detections for these techniques will help improve defenses for devices and networks against ransomware and other threats. As with any security research in Microsoft, this in-depth analysis of malware techniques informs the protection we provide through solutions like Microsoft Defender for Endpoint on Mac. We’re sharing this information with the rest of the community as a technical reference that researchers can use and build upon to understand Mac threats and improve protections.