ALIASES:

Trojan-Downloader.Win32.VB.bksu (Kaspersky); Trojan.Win32.Generic!BT (Sunbelt); Trojan horse Downloader.Generic13.BWGZ (AVG)

 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:

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

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

  TECHNICAL DETAILS

File Size: 20,480 bytes
File Type: EXE
Memory Resident: No
Initial Samples Received Date: 06 Jun 2014

Arrival Details

This Trojan 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 Trojan creates the following folders:

  • %System Root%\DOCUME~1
  • %System Root%\DOCUME~1\Wilbert
  • %User Profile%\LOCALS~1
  • %User Temp%\nsg8.tmp

(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.. %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003, or C:\Users\{user name} on Windows Vista and 7.. %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista and 7.)

Other System Modifications

This Trojan deletes the following files:

  • %User Temp%\nsl3.tmp
  • %User Temp%\nsg8.tmp

(Note: %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista and 7.)

It adds the following registry keys:

HKEY_CURRENT_USER\Software\TR2

HKEY_CLASSES_ROOT\AmiBs.Installer.1

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
AmiBs.Installer.1\CLSID

HKEY_CLASSES_ROOT\AmiBs.Installer

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
AmiBs.Installer\CurVer

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{A6FEED89-3BCD-4D19-9DC2-3E613A80A2A4}

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{A6FEED89-3BCD-4D19-9DC2-3E613A80A2A4}\ProgID

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{A6FEED89-3BCD-4D19-9DC2-3E613A80A2A4}\VersionIndependentProgID

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{A6FEED89-3BCD-4D19-9DC2-3E613A80A2A4}\Programmable

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{A6FEED89-3BCD-4D19-9DC2-3E613A80A2A4}\LocalServer32

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{A6FEED89-3BCD-4D19-9DC2-3E613A80A2A4}\TypeLib

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{A6FEED89-3BCD-4D19-9DC2-3E613A80A2A4}\Version

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
TypeLib\{1C1356DA-1E98-4810-A9F6-18D89BD1C0C0}

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
TypeLib\{1C1356DA-1E98-4810-A9F6-18D89BD1C0C0}\1.0

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
TypeLib\{1C1356DA-1E98-4810-A9F6-18D89BD1C0C0}\1.0\
FLAGS

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
TypeLib\{1C1356DA-1E98-4810-A9F6-18D89BD1C0C0}\1.0\
0

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
TypeLib\{1C1356DA-1E98-4810-A9F6-18D89BD1C0C0}\1.0\
0\win32

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
TypeLib\{1C1356DA-1E98-4810-A9F6-18D89BD1C0C0}\1.0\
HELPDIR

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Interface\{D54C859C-6066-4F31-8FE0-2AAEDCAE67D7}

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Interface\{D54C859C-6066-4F31-8FE0-2AAEDCAE67D7}\ProxyStubClsid

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Interface\{D54C859C-6066-4F31-8FE0-2AAEDCAE67D7}\ProxyStubClsid32

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Interface\{D54C859C-6066-4F31-8FE0-2AAEDCAE67D7}\TypeLib

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
ESENT\Process\MediaPlayer__4681_i155157354_il223

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
ESENT\Process\MediaPlayer__4681_i155157354_il223\
DEBUG

It adds the following registry entries:

HKEY_CURRENT_USER\Software\TR2
uni = "1"

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{A6FEED89-3BCD-4D19-9DC2-3E613A80A2A4}\LocalServer32
ServerExecutable = "%User Temp%\MediaPlayer__4681_i155157354_il223.exe"

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Interface\{D54C859C-6066-4F31-8FE0-2AAEDCAE67D7}\TypeLib
Version = "1.0"

It modifies the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\Eventlog\Application\
ESENT
EventMessageFile = "%System%\ESENT.dll"

(Note: The default value data of the said registry entry is {random values}.)

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\Eventlog\Application\
ESENT
CategoryMessageFile = "%System%\ESENT.dll"

(Note: The default value data of the said registry entry is {random values}.)

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\Eventlog\Application\
ESENT
CategoryCount = "1"

(Note: The default value data of the said registry entry is 10.)

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\Eventlog\Application\
ESENT
TypesSupported = "7"

(Note: The default value data of the said registry entry is 7.)

Dropping Routine

This Trojan drops the following files:

  • %User Temp%\Calculator.exe
  • %User Temp%\7za.exe
  • %User Temp%\a.7z
  • %User Temp%\nsg8.tmp\execDos.dll
  • %User Temp%\core.exe
  • %User Temp%\fix.exe

(Note: %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista and 7.)

Other Details

This Trojan connects to the following possibly malicious URL:

  • {BLOCKED}0.1
  • {BLOCKED}.251.163
  • {BLOCKED}.123.12
  • {BLOCKED}.61.26

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine: 9.700

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

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_CURRENT_USER\Software
    • TR2
  • In HKEY_CLASSES_ROOT
    • AmiBs.Installer.1
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\AmiBs.Installer.1
    • CLSID
  • In HKEY_CLASSES_ROOT
    • AmiBs.Installer
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\AmiBs.Installer
    • CurVer
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID
    • {A6FEED89-3BCD-4D19-9DC2-3E613A80A2A4}
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\{A6FEED89-3BCD-4D19-9DC2-3E613A80A2A4}
    • ProgID
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\{A6FEED89-3BCD-4D19-9DC2-3E613A80A2A4}
    • VersionIndependentProgID
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\{A6FEED89-3BCD-4D19-9DC2-3E613A80A2A4}
    • Programmable
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\{A6FEED89-3BCD-4D19-9DC2-3E613A80A2A4}
    • LocalServer32
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\{A6FEED89-3BCD-4D19-9DC2-3E613A80A2A4}
    • TypeLib
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\{A6FEED89-3BCD-4D19-9DC2-3E613A80A2A4}
    • Version
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\TypeLib
    • {1C1356DA-1E98-4810-A9F6-18D89BD1C0C0}
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\TypeLib\{1C1356DA-1E98-4810-A9F6-18D89BD1C0C0}
    • 1.0
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\TypeLib\{1C1356DA-1E98-4810-A9F6-18D89BD1C0C0}\1.0
    • FLAGS
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\TypeLib\{1C1356DA-1E98-4810-A9F6-18D89BD1C0C0}\1.0
    • 0
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\TypeLib\{1C1356DA-1E98-4810-A9F6-18D89BD1C0C0}\1.0\0
    • win32
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\TypeLib\{1C1356DA-1E98-4810-A9F6-18D89BD1C0C0}\1.0
    • HELPDIR
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Interface
    • {D54C859C-6066-4F31-8FE0-2AAEDCAE67D7}
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Interface\{D54C859C-6066-4F31-8FE0-2AAEDCAE67D7}
    • ProxyStubClsid
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Interface\{D54C859C-6066-4F31-8FE0-2AAEDCAE67D7}
    • ProxyStubClsid32
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Interface\{D54C859C-6066-4F31-8FE0-2AAEDCAE67D7}
    • TypeLib
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\ESENT\Process
    • MediaPlayer__4681_i155157354_il223
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\ESENT\Process\MediaPlayer__4681_i155157354_il223
    • DEBUG

Step 3

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\TR2
    • uni = "1"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\{A6FEED89-3BCD-4D19-9DC2-3E613A80A2A4}\LocalServer32
    • ServerExecutable = "%User Temp%\MediaPlayer__4681_i155157354_il223.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Interface\{D54C859C-6066-4F31-8FE0-2AAEDCAE67D7}\TypeLib
    • Version = "1.0"

Step 4

Restore these modified registry values

[ Learn More ]

Important:Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this only if you know how to or you can seek your system administrator's help. You may also check out this Microsoft article first before modifying your computer's registry.

  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\Eventlog\Application\ESENT
    • From: EventMessageFile = "%System%\ESENT.dll"
      To: EventMessageFile = ""{random values}""
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\Eventlog\Application\ESENT
    • From: CategoryMessageFile = "%System%\ESENT.dll"
      To: CategoryMessageFile = ""{random values}""
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\Eventlog\Application\ESENT
    • From: CategoryCount = "1"
      To: CategoryCount = ""10""
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\Eventlog\Application\ESENT
    • From: TypesSupported = "7"
      To: TypesSupported = ""7""

Step 5

Search and delete these components

[ Learn More ]
There may be some components 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.
  • %User Temp%\Calculator.exe
  • %User Temp%\7za.exe
  • %User Temp%\a.7z
  • %User Temp%\nsg8.tmp\execDos.dll
  • %User Temp%\core.exe
  • %User Temp%\fix.exe

Step 6

Search and delete these folders

[ Learn More ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden folders in the search result.
  • %System Root%\DOCUME~1
  • %System Root%\DOCUME~1\Wilbert
  • %User Profile%\LOCALS~1
  • %User Temp%\nsg8.tmp

Step 7

Scan your computer with your Trend Micro product to delete files detected as TROJ_SPNV.03C314. 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.

Step 8

Restore this file from backup only Microsoft-related files will be restored. If this malware/grayware also deleted files related to programs that are not from Microsoft, please reinstall those programs on you computer again.

  • %User Temp%\nsl3.tmp
  • %User Temp%\nsg8.tmp


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