Querying the I/O Communication Port

VMware uses virtual I/O ports for communication between the virtual machine and the host operating system to support functionality like copy and paste between the two systems. The port can be queried and compared with a magic number VMXh to identify the use of VMware.

Technique Identifiers

U1336 B0009.025

Evasion Categories

Sandbox Evasion

Code Snippets

Description

Source: https://gist.github.com/kooroshh/e4a303368555ea57f04f87e5630147b5

void CheckVM(void)
{
	unsigned int    a, b;

	__try {
		__asm {

			// save register values on the stack
			push eax
			push ebx
			push ecx
			push edx

			// perform fingerprint
			mov eax, 'VMXh' // VMware magic value (0x564D5868)
			mov ecx, 0Ah // special version cmd (0x0a)
			mov dx, 'VX' // special VMware I/O port (0x5658)

			in eax, dx // special I/O cmd

			mov a, ebx // data 
			mov b, ecx // data (eax gets also modified

			// restore register values from the stack
			pop edx
			pop ecx
			pop ebx
			pop eax
		}
	}
	__except (EXCEPTION_EXECUTE_HANDLER) {}

	if (a == 'VMXh') { // is the value equal to the VMware magic value?
		printf("Result  : VMware detected\nVersion : ");
		if (b == 1)
			printf("Express\n\n");
		else if (b == 2)
			printf("ESX\n\n");
		else if (b == 3)
			printf("GSX\n\n");
		else if (b == 4)
			printf("Workstation\n\n");
		else
			printf("unknown version\n\n");
	}
	else
		printf("Result  : Not Detected\n\n");
}

About Author Open Snippet

Author: Unprotect / Target Platform: Windows

Additional Resources

External Links

The resources provided below are associated links that will give you even more detailed information and research on current evasion technique. It is important to note that, while these resources may be helpful, it is important to exercise caution when following external links. As always, be careful when clicking on links from unknown sources, as they may lead to malicious content.

https://www.aldeid.com/wiki/VMXh-Magic-Value

Created

March 11, 2019

Last Revised

March 24, 2026