Analysis by: Anthony Joe Melgarejo

ALIASES:

BDS/Sinowal.thd (Antivir), W32/Sinowal.THD!tr.bdr (Fortinet), Backdoor.Win32.Sinowal (Ikarus), Backdoor.Sinowal (VBA32)

 PLATFORM:

Windows 2000, Windows Server 2003, Windows XP (32-bit, 64-bit), Windows Vista (32-bit, 64-bit), Windows 7 (32-bit, 64-bit)

 OVERALL RISK RATING:
 DAMAGE POTENTIAL:
 DISTRIBUTION POTENTIAL:
 REPORTED INFECTION:
 INFORMATION EXPOSURE:

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel: Downloaded from the Internet

This backdoor may be downloaded by other malware/grayware/spyware from remote sites.

It executes commands from a remote malicious user, effectively compromising the affected system.

  TECHNICAL DETAILS

File Size: 179,200 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 29 Oct 2013
Payload: Connects to URLs/IPs, Steals information, Downloads files

Arrival Details

This backdoor may be downloaded by other malware/grayware/spyware from remote sites.

Installation

This backdoor drops the following files:

  • %All Users Profile%\Application Data\{random number 1}\{random number}.dat - contains hex value of its file name
  • %All Users Profile%\Application Data\{random number 1}\{random number}.dll - contains hex value of its file name
  • %All Users Profile%\Application Data\{random number 1}\{dat name}.dat - config file
  • %All Users Profile%\Application Data\{random number 1}\{dll name}.dll - also detected as BKDR_SINOWAL.COP

(Note: %All Users Profile% is the All Users or Common profile folder, which is C:\Documents and Settings\All Users in Windows 2000, XP, and Server 2003, and C:\ProgramData in Windows Vista and 7.)

It adds the following mutexes to ensure that only one of its copies runs at any one time:

  • PJYTYOCEBHBSCAJFEJTLTHSCBHEBY
  • KDACHIQCQPAXYBVCXUPYXFYCSQWR
  • KDACHIQCQPAXYBVCXUPYXFYCSQWR-{number}

Autostart Technique

This backdoor adds the following registry entries to enable its automatic execution at every system startup:

HKEY_CLASSES_ROOT\CLSID\{GUID}\
InprocServer32
(Default) = "%All Users Profile%\Application Data\{random number 1}\{dll name}.dll"

HKEY_CURRENT_USER\Software\Classes\
CLSID\{GUID}\InprocServer32
(Default) = "%All Users Profile%\Application Data\{random number 1}\{dll name}.dll"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\ShellServiceObjectDelayLoad
{value name} = "{GUID}"

HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows NT\CurrentVersion\Windows
AppInit_DLLs = "%All Users Profile%\Application Data\{random number 1}\{dll name}.dll"

HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows NT\CurrentVersion\Windows
LoadAppInitDLLs = "1"

HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows NT\CurrentVersion\Windows
RequireSignedAppInit_DLLs = "0"

Backdoor Routine

This backdoor executes the following commands from a remote malicious user:

  • Download arbitrary files

It connects to the following URL(s) to send and receive commands from a remote malicious user:

  • http://{BLOCKED}stingmultiformat.org/search2?fr=altavista&itag=ody&q=443b40b41d25b91dd9a4104278083c14%2Cf4f535b835f5429b&kgs=1&kls=0&p={parameter}
  • http://{BLOCKED}.{BLOCKED}.109.201/search2?fr=altavista&itag=ody&q=443b40b41d25b91dd9a4104278083c14%2Cf4f535b835f5429b&kgs=1&kls=0&p={parameter}
  • http://www.{BLOCKED}rtsgm.com/search2?fr=altavista&itag=ody&q=443b40b41d25b91dd9a4104278083c14%2Cf4f535b835f5429b&kgs=1&kls=0&p={parameter}

It posts the following information to its command and control (C&C) server:

  • List of running processes
  • Applications installed in the system (found in HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall)

As of this writing, the said servers are currently inaccessible.

NOTES:

This backdoor suspends the thread of Trusteer Rapport program if it finds the said thread running in the processes of the following browsers:

  • opera.exe
  • chrome.exe
  • firefox.exe
  • iexplore.exe

It displays a message box with the following contents if the file avgui.exe is running in the system:

Title: Thank you
Message: Thank you for using AVG Product!

{dll name} can be any of the following:

  • mswd
  • mscc
  • msdr
  • msdd
  • msee
  • wsse
  • msseedir
  • lmbd
  • mmdd

{dat name} can be any of the following:

  • jdlr
  • elct
  • nudr
  • werr
  • qnud
  • xdor
  • ccdxmmde
  • vvve
  • kdkd
  • colu
  • uloc
  • drss
  • rrxx
  • du44
  • xes2
  • ii33
  • ned9
  • i3u4

{GUID} can be any of the following:

  • {A12BEDCC-A901-4203-B4F2-ADCB957D1887}
  • {212B3DCC-A901-4203-B4F2-ADCB957D1887}
  • {312BFDCE-A901-4203-B4F2-ADCB957D1887}
  • {F12BE2CC-A901-4203-B4F2-ADCB957D1887}
  • {312BED3C-A901-4203-B4F2-ADCB957D1887}
  • {118BEDCC-A901-4203-B4F2-ADCB957D1887}

{value name} can be any of the following:

  • MSCPY
  • CopierMircosoft
  • MSCopy
  • MicrosoftCopy
  • WindowsCopy
  • Copier

This backdoor executes its DLL component by using the following command:

%System%\cmd.exe /c %System%\regsvr32.exe /s "%All Users Profile%\Application Data\{dll name}.dll"

  SOLUTION

Minimum Scan Engine: 9.700
FIRST VSAPI PATTERN FILE: 10.394.02
FIRST VSAPI PATTERN DATE: 06 Nov 2013
VSAPI OPR PATTERN File: 10.395.00
VSAPI OPR PATTERN Date: 07 Nov 2013

Step 1

Before doing any scans, Windows XP, Windows Vista, and Windows 7 users must disable System Restore to allow full scanning of their computers.

Step 2

Scan your computer with your Trend Micro product and note files detected as BKDR_SINOWAL.COP

Step 3

Identify and delete files detected as BKDR_SINOWAL.COP using the Recovery Console

[ Learn More ]

Step 4

Delete this registry value

[ Learn More ]

Important: Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this step only if you know how or you can ask assistance from your system administrator. Else, check this Microsoft article first before modifying your computer's registry.

  • In HKEY_CLASSES_ROOT\CLSID\{GUID}\InprocServer32
    • (Default) = "%All Users Profile%\Application Data\{random number 1}\{dll name}.dll"
  • In HKEY_CURRENT_USER\Software\Classes\CLSID\{GUID}\InprocServer32
    • (Default) = "%All Users Profile%\Application Data\{random number 1}\{dll name}.dll"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\ShellServiceObjectDelayLoad
    • {value name} = "{GUID}"
  • In HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\CurrentVersion\Windows
    • AppInit_DLLs = "%All Users Profile%\Application Data\{random number 1}\{dll name}.dll"
  • In HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\CurrentVersion\Windows
    • LoadAppInitDLLs = "1"
  • In HKEY_LOCAL_MACHINE\Software\Microsoft\Windows NT\CurrentVersion\Windows
    • RequireSignedAppInit_DLLs = "0"

Step 5

Search and delete these files

[ Learn More ]
There may be some component files that are hidden. Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden files and folders in the search result.
  • %All Users Profile%\Application Data\{random number 1}\{random number}.dat - contains hex value of its file name
  • %All Users Profile%\Application Data\{random number 1}\{random number}.dll - contains hex value of its file name
  • %All Users Profile%\Application Data\{random number 1}\{dat name}.dat - config file

Step 6

Scan your computer with your Trend Micro product to delete files detected as BKDR_SINOWAL.COP. If the detected files have already been cleaned, deleted, or quarantined by your Trend Micro product, no further step is required. You may opt to simply delete the quarantined files. Please check this Knowledge Base page for more information.


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