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The second volume \\.\Hd2 is not mapped to a file, so when a computer is switched off, its contents is lost. Thus, it could be
used as a temporary or a cache storage. The data stored in \\.\Hd2 is encrypted the same way the first volume
s data.
Both volumes appear to be set up as FAT volumes.
An attempt to read the data from these volumes with the code below:
01 HANDLE hDisk = CreateFile(
\\\\.\\Hd1
02
GENERIC_READ,
03
FILE_SHARE_READ,
04
NULL,
05
OPEN_EXISTING,
06
0,
07
NULL);
08 BYTE lpBuffer[16384];
09 DWORD dwBytes;
10 if (hDisk)
11 {
12
ReadFile(hDisk, lpBuffer, 16384, &dwBytes, NULL);
13
// inspect the buffer
14
CloseHandle(hDisk);
15 }
This will produce the following results:
For \\.\Hd1:
0 1 2 3 4 5 6 7 8 9 A B C D E F 0123456789ABCDEF
00000000 EB 00 00 00 00 00 00 00 00 00 00 00 02 04 02 00 ................
00000010 02 00 02 00 00 F8 C8 00 20 00 02 00 01 00 00 00 ........ .......
00000020 FF 1F 03 00 80 00 29 E8 99 9B BA 4E 4F 20 4E 41 ......)....NO NA
00000030 4D 45 20 20 20 20 46 41 54 31 36 20 20 20 00 00 ME FAT16 ..
00000040 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
For \\.\Hd2:
0 1 2 3 4 5 6 7 8 9 A B C D E F 0123456789ABCDEF
00000000 EB 00 00 00 00 00 00 00 00 00 00 00 02 01 02 00 ................
00000010 02 00 02 FF 7F F8 7F 00 20 00 02 00 01 00 00 00 ........ .......
00000020 00 00 00 00 80 00 29 E8 99 9B BA 4E 4F 20 4E 41 ......)....NO NA
00000030 4D 45 20 20 20 20 46 41 54 31 36 20 20 20 00 00 ME FAT16 ..
00000040 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
The ability to keep its data on TrueCrypt-like volumes provides Snake with a powerful ability to exchange data with the usermode
DLL, as these volumes are accessible both from usermode and kernel mode.
Static analysis of the code reveals that the Snake driver uses virtual volumes to store its data and additional files on it.
For example, it stores its message queue in a file called:
\.\\Hd1\queue
The message queue indicates an asynchronous communication model between kernel mode driver and a usermode DLL,
e.g. to pass commands, configuration parameters, binary images of additional Snake components.
Other files that may also be found on the virtual volume are: klog, conlog, dump, rkng_inst.exe,
where rkng_inst.exe could be the name of the original dropper, and other log files could potentially contain executed command
outputs, intercepted keystrokes, and other output logs.
BAE Systems Applied Intelligence: Snake Rootkit Report 2014 21
64-BIT EDITIONS OF WINDOWS
The 64-bit version of Snake must deal with a number of additional security protections implemented in 64-bit editions of Microsoft
Windows, the most significant of which are kernel driver signature validation and Kernel Patch Protection (more commonly known as
PatchGuard).
PatchGuard is a feature of 64-bit Windows which aims to prevent modification of the Windows kernel, something that is often
performed by malware attempting to hide itself on an infected system. Although PatchGuard is successful at preventing kernel
patching once initialised, several published bypass approaches exist4,5. The technique used by Snake appears to be similar to these
approaches.
The driver signing policy enforced by all 64-bit versions of Windows from Vista onwards requires all kernel-mode drivers to be signed
with a valid digital signature. The Snake dropper contains both 32-bit and 64-bit unsigned drivers, and it can successfully load its
unsigned 64-bit driver on a 64-bit version of Windows XP
as driver signing is not enforced it does not have to resort to any tricks
under this OS version. In this case, in order to ensure the driver is loaded automatically at startup, the dropper can install the 64-bit
driver on 64-bit Windows XP in the same way it installs a 32-bit driver on a 32-bit version of Windows XP.
On 64-bit versions of Windows Vista and above it behaves differently. Firstly, the 64-bit unsigned driver file is created as usual:
%windows%\$NtUninstallQ817473$\fdisk.sys
However, the driver is not registered; what is registered instead is the dropper itself. To do that, the dropper first copies itself as:
%windows%\$NtUninstallQ817473$\fdisk_mon.exe
The dropper then registers itself as a service to ensure it starts every time Windows is booted, by creating the values:
ErrorControl = 0
Type = 16
Start = 2
ImagePath =
%SystemRoot%\$NtUninstallQ817473$\fdisk_mon.exe
ObjectName =
LocalSystem
WOW64 = 1
in the registry key:
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Ultra3
Now comes the most interesting part: does the dropper manage to load its 64-bit unsigned driver under 64-bit versions of Windows
Vista and later versions, such as 64-bit Windows 7/8? The answer: Yes, it does.
Does it resort to using bootkit technology, which has been used in the past to bypass protections to load unsigned 64-bit drivers?
The answer: No. Bootkits must overwrite the Master Boot Record (MBR) and antivirus products are well trained to catch that kind of
bad behavior.
The masterminds behind Snake rootkit seem to be well aware of this so what they resorted to instead is leveraging a vulnerability
in a well-known virtualization product called VirtualBox, a product made by Oracle which is widely used by researchers to analyse
malware. VirtualBox driver version 1.6.2 was released in June 2, 2008. Two months later, in August 2008, security researchers
reported that its main driver component, which is signed under the entity
innotek Gmbh
, contained a privilege escalation
vulnerability6.
In a nutshell, the VirtualBox software installs a driver called VBoxDrv. The driver is controlled with the Input/Ouput Control Codes
(32-bit values called IOCTL) passed along DeviceIoControl() API. One of the documented transfer methods that the system
uses to pass data between the caller of DeviceIoControl() API and the driver itself is called METHOD_NEITHER.