Cyber Risks · Cisco Talos

How does malware know the difference between the virtual world and the real world?

Summary: Cisco Talos describes how malware binaries carry code to detect virtual machines used for analysis, checking for VMware MAC address prefixes like 00:50:56 and 00:0C:29, registry keys such as the CWSandbox ProductId 76487-644-3177037-23510, and VMware device drivers including vmmouse.sys. Other techniques include reading the IDTR, GDTR and LDTR registers with the SIDT, SGDT and SLDT instructions, probing VMware's I/O port 0x5658, and checking for user-land debuggers via SystemKernelDebuggerInformation and ProcessDebugPort.

Bottom line: Malware that spots an analysis sandbox can simply withhold its malicious behavior, so a clean result from a virtual machine may mean the sample detected the lab rather than that it is harmless. Talos's countermeasures - skipping VMware Tools and editing the .vmx file - are manual steps that determine whether your analysis environment produces real findings.

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Topics
Malware
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