Ransomware Behavior on Windows Endpoint: An Analysis
Authors:   MyCERT, Cybersecurity Malaysia, Menara Cyber Axis, Jalan Impact, 63000 Cyberjaya, Selangor, Malaysia, Z. A. Zakaria Wira , Abdollah Mohd Faizal ,   Fakulti Teknologi Maklumat dan Komunikasi, Universiti Teknikal Malaysia Melaka, Hang Tuah Jaya, 76100 Durian Tunggal, Melaka, Malaysia, Abdollah Othman ,   Fakulti Teknologi Maklumat dan Komunikasi, Universiti Teknikal Malaysia Melaka, Hang Tuah Jaya, 76100 Durian Tunggal, Melaka, Malaysia, S.M.M S.M. Warusia Mohamed ,   Fakulti Teknologi Maklumat dan Komunikasi, Universiti Teknikal Malaysia Melaka, Hang Tuah Jaya, 76100 Durian Tunggal, Melaka, Malaysia
Published: December 2023

This paper provides a comprehensive examination of ransomware behavior on Windows endpoints, exploring the intrusion mechanisms, proliferation methods, and the mitigating strategies that can be employed. It provides a comparative analysis of several ransomware families and their effects on Windows systems, culminating with suggestions for future research directions in enhancing endpoint security against ransomware attacks. In the wake of a rising number of ransomware attacks worldwide, epitomized by the damaging disruptions to the Colonial Pipeline and the Irish Health Service Executive, the persistent threat of ransomware to critical infrastructure has never been more apparent. While Windows endpoints remain primary targets, these attacks have also highlighted a less explored but crucial aspect of ransomware behavior: the exploitation of Application Programming Interface (API) calls integral to the Windows operating system. This comprehensive study provides an exhaustive investigation into the interplay between ransomware and Windows APIs, emphasizing the patterns of invocation and manipulative misuse by various ransomware families. By investigating specific API calls, such as the CryptEncrypt function in the Cryptography API for encryption, and the CreateFile and WriteFile functions in the File API for file system interaction, we illuminate the mechanisms by which ransomware carry out their damaging actions. Further, using the real-world examples drawn from the Colonial Pipeline and Irish Health Service Executive incidents, among others, the study shows how these API calls were manipulated during actual ransomware attacks. In these cases, ransomware like DarkSide and Conti used Windows APIs not just for the primary tasks of encryption and file system manipulation, but also for achieving network communication, maintaining persistence, and even thwarting detection. By presenting a comparative analysis of API call sequences in both benign and ransomware-infected Windows environments, this study serves as a critical exploration into the behavior of these malicious entities. The different patterns observed provide us with valuable insights into their operational strategies and offer opportunities for the development of detection heuristics. The insights derived from this research contribute significantly to our understanding of the behavior patterns of recent, high-profile ransomware attacks. In turn, this work aims to guide the evolution of more sophisticated, behavior-based detection mechanisms, thus strengthening the security posture of Windows endpoints. Ultimately, this study underscores the need for continuous research into API call patterns, as the cybersecurity landscape continues to face dynamic and increasingly sophisticated threats.