ALIASES:

Backdoor:Win32/Zegost.B (Microsoft); Generic Dropper.kr (McAfee); Suspicious.Graybird.1 (Symantec); Trojan-Dropper.Win32.Binder.rz (Kaspersky); Trojan-Dropper.Win32.Binder.rz (v) (Sunbelt); Trojan.Generic.2099004 (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: 211,968 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 25 Apr 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.

Installation

This Trojan creates the following folders:

  • %System Root%\Documents and Settings\Local User

(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)

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\{21E9C5D3-EBFF-11CD-B6FD-00AA00B4E22A}
StubPath = "%Program Files%\DBS.EXE"

Other System Modifications

This Trojan adds the following registry keys:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Active Setup\Installed Components\{21E9C5D3-EBFF-11CD-B6FD-00AA00B4E22A}

It adds the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\6to4
InstallModule = "%Program Files%\common files\microsoft shared\msinfo\server.exe"

It modifies the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\6to4
Type = "4"

(Note: The default value data of the said registry entry is 20.)

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\6to4
Description = "{random characters}"

(Note: The default value data of the said registry entry is Provides DDNS name registration and automatic IPv6 connectivity over an IPv4 network. If this service is stopped, other computers may not be able to reach it by name and the machine will only have IPv6 connectivity if it is connected to a native IPv6 network. If this service is disabled, any other services that explicitly depend on this service will fail to start..)

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\6to4\Parameters
ServiceDll = "%User Profile%\userdata.dll"

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

It deletes the following registry keys:

HKEY_CURRENT_USER\SOFTWARE\Microsoft\
Active Setup\Installed Components\{21E9C5D3-EBFF-11CD-B6FD-00AA00B4E22A}

Dropping Routine

This Trojan drops the following files:

  • %Program Files%\common files\microsoft shared\msinfo\MyServer.jpg
  • %Program Files%\common files\microsoft shared\msinfo\server.jpg
  • %Program Files%\common files\microsoft shared\msinfo\δÃüÃû.jpg
  • %User Profile%\userdata.dll
  • %Program Files%\DBS.EXE

(Note: %Program Files% is the default Program Files folder, usually C:\Program Files in Windows 2000, Server 2003, and XP (32-bit), Vista (32-bit), and 7 (32-bit), or C:\Program Files (x86) in Windows XP (64-bit), Vista (64-bit), and 7 (64-bit).. %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.)

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine: 9.200

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

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\Active Setup\Installed Components
    • {21E9C5D3-EBFF-11CD-B6FD-00AA00B4E22A}

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\{21E9C5D3-EBFF-11CD-B6FD-00AA00B4E22A}
    • StubPath = "%Program Files%\DBS.EXE"
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\6to4
    • InstallModule = "%Program Files%\common files\microsoft shared\msinfo\server.exe"

Step 5

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\6to4
    • From: Type = "4"
      To: Type = ""20""
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\6to4
    • From: Description = "{random characters}"
      To: Description = ""Provides DDNS name registration and automatic IPv6 connectivity over an IPv4 network. If this service is stopped, other computers may not be able to reach it by name and the machine will only have IPv6 connectivity if it is connected to a native IPv6 network. If this service is disabled, any other services that explicitly depend on this service will fail to start.""
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\6to4\Parameters
    • From: ServiceDll = "%User Profile%\userdata.dll"
      To: ServiceDll = ""{random values}""

Step 6

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.
  • %Program Files%\common files\microsoft shared\msinfo\MyServer.jpg
  • %Program Files%\common files\microsoft shared\msinfo\server.jpg
  • %Program Files%\common files\microsoft shared\msinfo\δÃüÃû.jpg
  • %User Profile%\userdata.dll
  • %Program Files%\DBS.EXE

Step 7

Search and delete this folder

[ 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%\Documents and Settings\Local User

Step 8

Restart in normal mode and scan your computer with your Trend Micro product for files detected as TROJ_DELF.SMV. 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 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
    • {21E9C5D3-EBFF-11CD-B6FD-00AA00B4E22A}


Did this description help? Tell us how we did.