Unravelling .NET with the Help of WinDBG
Summary: Cisco Talos researchers Paul Rascagneres and Warren Mercer described using WinDBG with Microsoft's SOS extension to analyze .NET malware, loading the extension from CLR.dll for .NET 4 and mscorwks for .NET 2 and 3. They set breakpoints on Process.Start, WebClient.DownloadFile and Assembly.Load to capture arguments and dump unpacked binaries, covering packers that decode Base64 strings with an XOR key or decrypt with AES before loading a PE32 payload via Assembly.Load().
What you should know: The unpacked payload sits in memory as a byte array passed to Assembly.Load(), so a packer using XOR or AES never needs to write a readable executable to disk for analysts to collect.
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- Topics
- Malware
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