VMCPUID

Created the Monday 11 March 2019. Updated 1 year, 7 months ago.

The VMCPUID instruction is a sophisticated mechanism often employed by malware to ascertain if it is operating within a virtual environment.

This instruction is part of the x86 architecture's virtual machine extensions (VMX) and is designed to provide information about the capabilities and status of the virtual machine.

By using VMCPUID, malware can adapt its behavior based on the context in which it is running, thus adding an additional layer of complexity to its detection and mitigation. Essentially, it serves as a telltale indicator, aiding malware in identifying virtualization-based security measures or sandboxing environments

Technique Identifiers

U1322 B0009.037

Technique Tags

VMCPUID instruction malware detection virtual environment x86 architecture

Code Snippets

Description

This C++ program uses the Windows and Intel intrinsic headers to check if it's running in a Microsoft Hyper-V virtual environment. It defines a union called CpuFeaturesEcx, which is used to map out the CPU features reported by the cpuid instruction, specifically the contents of the ECX register. These include various instruction sets, such as SSE3, SMX, and AESNI.

The function IsHyperV() uses the __cpuid function intrinsic to get the processor features and checks for the existence of Hyper-V by examining the hypervisor brand identification reported by cpuid with the leaf parameter 0x40000001. If the returned value is more than or equal to 4000, it indicates the presence of Hyper-V.

In the main() function, it calls the IsHyperV() function and outputs whether the current environment is a Hyper-V or not. If IsHyperV() returns true, it prints "Hyper-V True"; otherwise, it prints "Hyper-V False".

#include <Windows.h>
#include <iostream>
#include <intrin.h>

/// See: Feature Information Returned in the ECX Register
union CpuFeaturesEcx {
    ULONG32 all;
    struct {
        ULONG32 sse3 : 1;       //!< [0] Streaming SIMD Extensions 3 (SSE3)
        ULONG32 pclmulqdq : 1;  //!< [1] PCLMULQDQ
        ULONG32 dtes64 : 1;     //!< [2] 64-bit DS Area
        ULONG32 monitor : 1;    //!< [3] MONITOR/WAIT
        ULONG32 ds_cpl : 1;     //!< [4] CPL qualified Debug Store
        ULONG32 vmx : 1;        //!< [5] Virtual Machine Technology
        ULONG32 smx : 1;        //!< [6] Safer Mode Extensions
        ULONG32 est : 1;        //!< [7] Enhanced Intel Speedstep Technology
        ULONG32 tm2 : 1;        //!< [8] Thermal monitor 2
        ULONG32 ssse3 : 1;      //!< [9] Supplemental Streaming SIMD Extensions 3
        ULONG32 cid : 1;        //!< [10] L1 context ID
        ULONG32 sdbg : 1;       //!< [11] IA32_DEBUG_INTERFACE MSR
        ULONG32 fma : 1;        //!< [12] FMA extensions using YMM state
        ULONG32 cx16 : 1;       //!< [13] CMPXCHG16B
        ULONG32 xtpr : 1;       //!< [14] xTPR Update Control
        ULONG32 pdcm : 1;       //!< [15] Performance/Debug capability MSR
        ULONG32 reserved : 1;   //!< [16] Reserved
        ULONG32 pcid : 1;       //!< [17] Process-context identifiers
        ULONG32 dca : 1;        //!< [18] prefetch from a memory mapped device
        ULONG32 sse4_1 : 1;     //!< [19] SSE4.1
        ULONG32 sse4_2 : 1;     //!< [20] SSE4.2
        ULONG32 x2_apic : 1;    //!< [21] x2APIC feature
        ULONG32 movbe : 1;      //!< [22] MOVBE instruction
        ULONG32 popcnt : 1;     //!< [23] POPCNT instruction
        ULONG32 reserved3 : 1;  //!< [24] one-shot operation using a TSC deadline
        ULONG32 aes : 1;        //!< [25] AESNI instruction
        ULONG32 xsave : 1;      //!< [26] XSAVE/XRSTOR feature
        ULONG32 osxsave : 1;    //!< [27] enable XSETBV/XGETBV instructions
        ULONG32 avx : 1;        //!< [28] AVX instruction extensions
        ULONG32 f16c : 1;       //!< [29] 16-bit floating-point conversion
        ULONG32 rdrand : 1;     //!< [30] RDRAND instruction
        ULONG32 not_used : 1;   //!< [31] Always 0 (a.k.a. HypervisorPresent)
    } fields;
};
static_assert(sizeof(CpuFeaturesEcx) == 4, "Size check");

const bool IsHyperV()
{
	int cpu_info[4] = {};
	__cpuid(cpu_info, 1);
	const CpuFeaturesEcx cpu_features = { static_cast<ULONG_PTR>(cpu_info[2]) };
    __cpuid(cpu_info, 0x40000001);
    DWORD vid = 0;
    vid = (DWORD)cpu_info[0];
    return (vid >= 4000);
}

int main()
{
    if (IsHyperV()) {
        std::cout << "Hyper-v Ture" << std::endl;
    }
    else {
        std::cout << "Hyper-v Flase" << std::endl;
    }
    return 0;
}

About Author Open Snippet

Author: 一半人生 / Target Platform: Windows

Additional Resources

External Links

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https://www.cert.pl/en/news/single/necurs-hybrid-spam-botnet/