On April 14, 2017, the Shadow Brokers Group released the FUZZBUNCH framework, an exploitation toolkit for Microsoft Windows. The toolkit was allegedly written by the Equation Group, a highly sophisticated threat actor suspected of being tied to the United States National Security Agency (NSA). The framework included ETERNALBLUE, a remote kernel exploit originally targeting the Server Message Block (SMB) service on Microsoft Windows XP (Server 2003) and Microsoft Windows 7 (Server 2008 R2). In this paper, the RiskSense Cyber Security Research team analyzes how using wrong-sized CPU registers leads to a seemingly innocuous mathematical miscalculation. This causes a chain reaction domino effect ultimately culminating in code execution, making ETERNALBLUE one of the most complex exploits ever written. They will discuss what was necessary to port the exploit to Microsoft Windows 10, and future mitigations Microsoft has already deployed, which can prevent vulnerabilities of this class from being exploited in the future. The FUZZBUNCH version of the exploit contains an Address Space Layout Randomization (ASLR) bypass, and the Microsoft Windows 10 version required an additional Data Execution Prevention (DEP) bypass not needed in the original exploit.
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