ALIASES:

Trojan:Win32/Meredrop (Microsoft); generic!bg.ftk (McAfee); PAK:UPX, Trojan-Downloader.Win32.Small.lh (Kaspersky); Trojan-Downloader.Win32.Small (Sunbelt); Trojan.Downloader.Small.LH (FSecure)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

 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: 419,444 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 11 Jul 2012

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.

Autostart Technique

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

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Active Setup\Installed Components\{5Y99AE78-58TT-11dW-BE53-Y67078979Y}
StubPath = "%System%\sservice.exe"

It modifies the following registry entries to ensure it automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
Shell = "Explorer.exe %System%\Fservice.exe"

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

Other System Modifications

This Trojan deletes the following files:

  • %System%\sservice.exe
  • %Windows%\services.exe
  • %System%\fService.exe

(Note: %System% is the Windows system folder, which is usually C:\Windows\System on Windows 98 and ME, C:\WINNT\System32 on Windows NT and 2000, or C:\Windows\System32 on Windows XP and Server 2003.. %Windows% is the Windows folder, which is usually C:\Windows or C:\WINNT.)

It adds the following registry keys:

HKEY_CURRENT_USER\SOFTWARE\Microsoft DirectX\
WinSettings

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\policies\
Explorer\Run

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Active Setup\Installed Components\{5Y99AE78-58TT-11dW-BE53-Y67078979Y}

It adds the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft DirectX\
WinSettings
Bulas = "1"

HKEY_CURRENT_USER\Software\Microsoft DirectX\
WinSettings
FW_KILL = "0"

HKEY_CURRENT_USER\Software\Microsoft DirectX\
WinSettings
XP_FW_Disable = "1"

HKEY_CURRENT_USER\Software\Microsoft DirectX\
WinSettings
XP_SYS_Recovery = "1"

HKEY_CURRENT_USER\Software\Microsoft DirectX\
WinSettings
Kurban_Ismi = "udrud07"

HKEY_CURRENT_USER\Software\Microsoft DirectX\
WinSettings
Mail = "bndts33othuAx`inn/bnl"

HKEY_CURRENT_USER\Software\Microsoft DirectX\
WinSettings
Port = "4001"

HKEY_CURRENT_USER\Software\Microsoft DirectX\
WinSettings
Sifre = "bnt{ho"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\policies\
Explorer\Run
DirectX For Microsoft® Windows = "%System%\Fservice.exe"

It deletes the following registry keys:

HKEY_CURRENT_USER\Software\Microsoft\
Active Setup\Installed Components\{5Y99AE78-58TT-11dW-BE53-Y67078979Y}

Dropping Routine

This Trojan drops the following files:

  • %User Temp%\ALBUM.shs
  • %System%\Fservice.exe
  • %System%\sservice.exe
  • %Windows%\services.exe
  • %System%\fService.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.. %System% is the Windows system folder, which is usually C:\Windows\System on Windows 98 and ME, C:\WINNT\System32 on Windows NT and 2000, or C:\Windows\System32 on Windows XP and Server 2003.. %Windows% is the Windows folder, which is usually C:\Windows or C:\WINNT.)

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine: 9.200

Step 1

For Windows XP and Windows Server 2003 users, before doing any scans, please make sure you disable System Restore to allow full scanning of your computer.

Step 2

Identify and delete files detected as TROJ_SMALL.BIM using either the Startup Disk or Recovery Console

[ Learn More ]

Step 3

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\Microsoft DirectX
    • WinSettings
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\Explorer
    • Run
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Active Setup\Installed Components
    • {5Y99AE78-58TT-11dW-BE53-Y67078979Y}

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_LOCAL_MACHINE\SOFTWARE\Microsoft\Active Setup\Installed Components\{5Y99AE78-58TT-11dW-BE53-Y67078979Y}
    • StubPath = "%System%\sservice.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft DirectX\WinSettings
    • Bulas = "1"
  • In HKEY_CURRENT_USER\Software\Microsoft DirectX\WinSettings
    • FW_KILL = "0"
  • In HKEY_CURRENT_USER\Software\Microsoft DirectX\WinSettings
    • XP_FW_Disable = "1"
  • In HKEY_CURRENT_USER\Software\Microsoft DirectX\WinSettings
    • XP_SYS_Recovery = "1"
  • In HKEY_CURRENT_USER\Software\Microsoft DirectX\WinSettings
    • Kurban_Ismi = "udrud07"
  • In HKEY_CURRENT_USER\Software\Microsoft DirectX\WinSettings
    • Mail = "bndts33othuAx`inn/bnl"
  • In HKEY_CURRENT_USER\Software\Microsoft DirectX\WinSettings
    • Port = "4001"
  • In HKEY_CURRENT_USER\Software\Microsoft DirectX\WinSettings
    • Sifre = "bnt{ho"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\Explorer\Run
    • DirectX For Microsoft® Windows = "%System%\Fservice.exe"

Step 5

Restore this modified 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_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
    • From: Shell = "Explorer.exe %System%\Fservice.exe"
      To: Shell = ""Explorer.exe""

Step 6

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.
  • %User Temp%\ALBUM.shs
  • %System%\Fservice.exe
  • %System%\sservice.exe
  • %Windows%\services.exe
  • %System%\fService.exe

Step 7

Scan your computer with your Trend Micro product to delete files detected as TROJ_SMALL.BIM. 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.

  • %System%\sservice.exe
  • %Windows%\services.exe
  • %System%\fService.exe

Step 9

Restore these deleted registry keys/values from backup

*Note: Only Microsoft-related keys/values will be restored. If the malware/grayware also deleted registry keys/values related to programs that are not from Microsoft, please reinstall those programs on your computer.

  • In HKEY_CURRENT_USER\Software\Microsoft\Active Setup\Installed Components
    • {5Y99AE78-58TT-11dW-BE53-Y67078979Y}


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