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BKDR_SEDNIT.SM

October 14, 2013
 Analysis by: Alvin Bacani
 ALIASES:

Troj/Nvspy-A (Sophos)

 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, Dropped by other malware

This backdoor arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

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

  TECHNICAL DETAILS

Ports:

Port 80

File Size:

37,376 bytes

File Type:

DLL

Memory Resident:

Yes

Initial Samples Received Date:

30 Sep 2013

Payload:

Compromises system security

Arrival Details

This backdoor arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

Installation

This backdoor drops the following files:

  • %System%\netui.dll - detected as BKDR_SEDNIT.SM

(Note: %System% is the Windows system folder, which is usually C:\Windows\System32.)

Autostart Technique

This backdoor registers itself as a system service to ensure its automatic execution at every system startup by adding the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\SvcHost\
NtShvcs
CoInitializeSecurityParam = "0"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\SvcHost
NtShvcs = "Network User Interface"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Network User Interface
Type = "110"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Network User Interface
Start = "02"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Network User Interface
ErrorControl = "01"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Network User Interface
ImagePath = "%system%\svchost.exe -k NtShvcs"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Network User Interface
DisplayName = "Network User Interface"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Network User Interface
ObjectName = "LocalSystem"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Network User Interface
Description = "Provides user network interface service for secure connections"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Network User Interface\Parameters
ServiceDll = "%system%\netui.dll"

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\Network User Interface\Parameters
ServiceDllUnloadOnStop = "01"

Other System Modifications

This backdoor adds the following registry entries as part of its installation routine:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer
IP = "{Encrypted Binary Data, includes IP address for C&C}"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Explorer
IP = "{Encrypted Binary Data, includes IP address for C&C}"

Backdoor Routine

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

  • perform keylogging on the affected system
  • send collected data
  • download/execute files

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

  • {BLOCKED}.55.146 port 80
  • {BLOCKED}.115.178 port 80

Other Details

This backdoor drops the following file(s)/component(s):

  • %Temp%\nvgdata.dat
  • %Temp%\nvsdata.dat

(Note: %Temp% is the Windows Temporary folder, which is usually C:\Windows\Temp.)

  SOLUTION

Minimum Scan Engine:

9.300

FIRST VSAPI PATTERN FILE:

10.310.04

FIRST VSAPI PATTERN DATE:

30 Sep 2013

VSAPI OPR PATTERN File:

10.311.00

VSAPI OPR PATTERN Date:

01 Oct 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

Restart in Safe Mode

[ Learn More ]

Step 3

Search and delete this file

[ Learn More ]
There may be some 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.  
  • %system%\netui.dll
  • %Temp%\nvgdata.dat
  • %Temp%\nvsdata.dat

Step 4

Delete this registry key

[ 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_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\SvcHost
    • NtShvcs
  • In HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services
    • Network User Interface

Step 5

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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer
    • IP = {Encrypted Binary Data, includes IP address for C&C}
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer
    • IP = {Encrypted Binary Data, includes IP address for C&C}
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\SvcHost
    • NtShvcs = Network User Interface

Step 6

Restart in normal mode and scan your computer with your Trend Micro product for files detected as BKDR_SEDNIT.SM. 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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