BKDR_SMALLDOO.LF
Trojan:Win32/Meredrop (Microsoft); BackDoor-DVC (McAfee); Infostealer.Gampass (Symantec); ARC:EmbeddedEXE, ARC:[data0000]:Embedded (Kaspersky); Trojan.Win32.Generic!SB.0 (Sunbelt); Trojan.Generic.2100576 (FSecure)
Windows 2000, Windows, XP, Windows Server 2003
Threat Type: Backdoor
Destructiveness: No
Encrypted:
In the wild: Yes
OVERVIEW
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.
TECHNICAL DETAILS
1,472,539 bytes
EXE
No
16 Dec 2011
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 creates the following folders:
- %User Temp%\E_N4
(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 System Modifications
This backdoor adds the following registry keys:
HKEY_CLASSES_ROOT\CLSID\{248DD896-BB45-11CF-9ABC-0080C7E7B78D}
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{248DD896-BB45-11CF-9ABC-0080C7E7B78D}\InprocServer32
HKEY_CLASSES_ROOT\MSWinsock.Winsock
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
MSWinsock.Winsock\CLSID
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
MSWinsock.Winsock\CurVer
HKEY_CLASSES_ROOT\MSWinsock.Winsock.1
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
MSWinsock.Winsock.1\CLSID
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{248DD896-BB45-11CF-9ABC-0080C7E7B78D}\VersionIndependentProgID
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{248DD896-BB45-11CF-9ABC-0080C7E7B78D}\ProgID
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{248DD896-BB45-11CF-9ABC-0080C7E7B78D}\TypeLib
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{248DD896-BB45-11CF-9ABC-0080C7E7B78D}\Version
HKEY_CLASSES_ROOT\CLSID\{248DD897-BB45-11CF-9ABC-0080C7E7B78D}
InprocServer32
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
TypeLib\{248DD890-BB45-11CF-9ABC-0080C7E7B78D}
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
TypeLib\{248DD890-BB45-11CF-9ABC-0080C7E7B78D}\1.0
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
TypeLib\{248DD890-BB45-11CF-9ABC-0080C7E7B78D}\1.0\
0
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
TypeLib\{248DD890-BB45-11CF-9ABC-0080C7E7B78D}\1.0\
HELPDIR
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Interface\{248DD892-BB45-11CF-9ABC-0080C7E7B78D}
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Interface\{248DD892-BB45-11CF-9ABC-0080C7E7B78D}\ProxyStubClsid32
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Interface\{248DD892-BB45-11CF-9ABC-0080C7E7B78D}\TypeLib
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Interface\{248DD893-BB45-11CF-9ABC-0080C7E7B78D}
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Interface\{248DD893-BB45-11CF-9ABC-0080C7E7B78D}\ProxyStubClsid32
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Interface\{248DD893-BB45-11CF-9ABC-0080C7E7B78D}\TypeLib
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{248DD896-BB45-11CF-9ABC-0080C7E7B78D}\Control
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{248DD896-BB45-11CF-9ABC-0080C7E7B78D}\MiscStatus
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{248DD896-BB45-11CF-9ABC-0080C7E7B78D}\MiscStatus\
1
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{248DD896-BB45-11CF-9ABC-0080C7E7B78D}\ToolboxBitmap32
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{248DD897-BB45-11CF-9ABC-0080C7E7B78D}\InprocServer32
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
TypeLib\{248DD890-BB45-11CF-9ABC-0080C7E7B78D}\1.0\
FLAGS
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
TypeLib\{248DD890-BB45-11CF-9ABC-0080C7E7B78D}\1.0\
0\win32
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Interface\{248DD892-BB45-11CF-9ABC-0080C7E7B78D}\ProxyStubClsid
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Interface\{248DD893-BB45-11CF-9ABC-0080C7E7B78D}\ProxyStubClsid
It adds the following registry entries:
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{248DD896-BB45-11CF-9ABC-0080C7E7B78D}\InprocServer32
ThreadingModel = "Apartment"
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Interface\{248DD892-BB45-11CF-9ABC-0080C7E7B78D}\TypeLib
Version = "1.0"
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Interface\{248DD893-BB45-11CF-9ABC-0080C7E7B78D}\TypeLib
Version = "1.0"
It deletes the following registry keys:
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{248DD896-BB45-11CF-9ABC-0080C7E7B78D}
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{248DD897-BB45-11CF-9ABC-0080C7E7B78D}
Dropping Routine
This backdoor drops the following files:
- %User Temp%\´Ï´Ï5.1Ãâ·Ñ°æ.exe
- %User Temp%\1.exe
- %User Temp%\E_N4\krnln.fnr
- %System%\dnfsafe.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.. %System% is the Windows system folder, which is usually C:\Windows\System32.)
This report is generated via an automated analysis system.
SOLUTION
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
Delete this registry key
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
- {248DD896-BB45-11CF-9ABC-0080C7E7B78D}
- In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\{248DD896-BB45-11CF-9ABC-0080C7E7B78D}
- InprocServer32
- In HKEY_CLASSES_ROOT
- MSWinsock.Winsock
- In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\MSWinsock.Winsock
- CLSID
- In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\MSWinsock.Winsock
- CurVer
- In HKEY_CLASSES_ROOT
- MSWinsock.Winsock.1
- In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\MSWinsock.Winsock.1
- CLSID
- In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\{248DD896-BB45-11CF-9ABC-0080C7E7B78D}
- VersionIndependentProgID
- In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\{248DD896-BB45-11CF-9ABC-0080C7E7B78D}
- ProgID
- In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\{248DD896-BB45-11CF-9ABC-0080C7E7B78D}
- TypeLib
- In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\{248DD896-BB45-11CF-9ABC-0080C7E7B78D}
- Version
- In HKEY_CLASSES_ROOT\CLSID
- {248DD897-BB45-11CF-9ABC-0080C7E7B78D}
- In
- InprocServer32
- In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\TypeLib
- {248DD890-BB45-11CF-9ABC-0080C7E7B78D}
- In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\TypeLib\{248DD890-BB45-11CF-9ABC-0080C7E7B78D}
- 1.0
- In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\TypeLib\{248DD890-BB45-11CF-9ABC-0080C7E7B78D}\1.0
- 0
- In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\TypeLib\{248DD890-BB45-11CF-9ABC-0080C7E7B78D}\1.0
- HELPDIR
- In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Interface
- {248DD892-BB45-11CF-9ABC-0080C7E7B78D}
- In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Interface\{248DD892-BB45-11CF-9ABC-0080C7E7B78D}
- ProxyStubClsid32
- In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Interface\{248DD892-BB45-11CF-9ABC-0080C7E7B78D}
- TypeLib
- In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Interface
- {248DD893-BB45-11CF-9ABC-0080C7E7B78D}
- In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Interface\{248DD893-BB45-11CF-9ABC-0080C7E7B78D}
- ProxyStubClsid32
- In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Interface\{248DD893-BB45-11CF-9ABC-0080C7E7B78D}
- TypeLib
- In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\{248DD896-BB45-11CF-9ABC-0080C7E7B78D}
- Control
- In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\{248DD896-BB45-11CF-9ABC-0080C7E7B78D}
- MiscStatus
- In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\{248DD896-BB45-11CF-9ABC-0080C7E7B78D}\MiscStatus
- 1
- In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\{248DD896-BB45-11CF-9ABC-0080C7E7B78D}
- ToolboxBitmap32
- In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\{248DD897-BB45-11CF-9ABC-0080C7E7B78D}
- InprocServer32
- In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\TypeLib\{248DD890-BB45-11CF-9ABC-0080C7E7B78D}\1.0
- FLAGS
- In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\TypeLib\{248DD890-BB45-11CF-9ABC-0080C7E7B78D}\1.0\0
- win32
- In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Interface\{248DD892-BB45-11CF-9ABC-0080C7E7B78D}
- ProxyStubClsid
- In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Interface\{248DD893-BB45-11CF-9ABC-0080C7E7B78D}
- ProxyStubClsid
Step 3
Delete this registry value
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\Classes\CLSID\{248DD896-BB45-11CF-9ABC-0080C7E7B78D}\InprocServer32
- ThreadingModel="Apartment"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Interface\{248DD892-BB45-11CF-9ABC-0080C7E7B78D}\TypeLib
- Version="1.0"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Interface\{248DD893-BB45-11CF-9ABC-0080C7E7B78D}\TypeLib
- Version="1.0"
Step 4
Search and delete this folder
Step 5
Search and delete these components
- %User Temp%\´Ï´Ï5.1Ãâ·Ñ°æ.exe
- %User Temp%\1.exe
- %User Temp%\E_N4\krnln.fnr
- %System%\dnfsafe.exe
Step 6
Scan your computer with your Trend Micro product to delete files detected as BKDR_SMALLDOO.LF. 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 7
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_LOCAL_MACHINE\SOFTWARE\Classes\CLSID
- {248DD896-BB45-11CF-9ABC-0080C7E7B78D}
- In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID
- {248DD897-BB45-11CF-9ABC-0080C7E7B78D}
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