TROJ_OBFUSCA.DCB
Trojan:Win32/Tracur.Q (Microsoft); Generic Downloader.gu (McAfee); Trojan.Gen (Symantec); Trojan.Win32.Obfuscated.alrp (Kaspersky); Trojan.Win32.Generic!BT (Sunbelt); Gen:Variant.Kazy.26487 (FSecure)
Windows 2000, Windows XP, Windows Server 2003
![](/vinfo/imgFiles/legend.jpg)
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
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 drops the following copies of itself into the affected system:
- %System%\pidgen32.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.)
Autostart Technique
This Trojan registers itself as a BHO to ensure its automatic execution every time Internet Explorer is used by adding the following registry keys:
HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Browser Helper Objects\{57BEEE44-EE22-E631-FB0D-11C618C211B0}
Other System Modifications
This Trojan adds the following registry keys:
HKEY_CLASSES_ROOT\CLSID\{57BEEE44-EE22-E631-FB0D-11C618C211B0}
HKEY_CLASSES_ROOT\CLSID\{57BEEE44-EE22-E631-FB0D-11C618C211B0}\
InProcServer32
It adds the following registry entries:
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\SharedAccess\Parameters\
FirewallPolicy\DomainProfile\AuthorizedApplications\
List
%System%\pidgen32.exe = "%System%\pidgen32.exe:*:Enabled:Windows Update Service"
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile\AuthorizedApplications\
List
%System%\pidgen32.exe = "%System%\pidgen32.exe:*:Enabled:Windows Update Service"
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Explorer
f0bdff95 = "{random values}"
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Windows
LoadAppInit_DLLs = "1"
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{57BEEE44-EE22-E631-FB0D-11C618C211B0}\InProcServer32
ThreadingModel = "Apartment"
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Explorer\
Browser Helper Objects\{57BEEE44-EE22-E631-FB0D-11C618C211B0}
NoExplorer = "1"
It modifies the following registry entries:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Windows
AppInit_Dlls = "%System%\strmfilt32.dll"
It deletes the following registry keys:
HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows\CurrentVersion\{B6FB50C5-70BB-4b1e-97E7-64B307776E8A}
Dropping Routine
This Trojan drops the following files:
- %System%\avtapi32.dll
- %System%\strmfilt32.dll
- %System%\020000004d8102a01270P.manifest
- %System%\020000004d8102a01270C.manifest
- %System%\020000004d8102a01270O.manifest
- %System%\020000004d8102a01270S.manifest
- %System%\msprivs32.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.)
Other Details
This Trojan connects to the following possibly malicious URL:
- http://{BLOCKED}.153.48/{random path}
This report is generated via an automated analysis system.
SOLUTION
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
Close all opened browser windows
Step 3
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
- {57BEEE44-EE22-E631-FB0D-11C618C211B0}
- In HKEY_CLASSES_ROOT\CLSID\{57BEEE44-EE22-E631-FB0D-11C618C211B0}
- InProcServer32
Step 4
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\SYSTEM\ControlSet001\Services\SharedAccess\Parameters\FirewallPolicy\DomainProfile\AuthorizedApplications\List
- %System%\pidgen32.exe = "%System%\pidgen32.exe:*:Enabled:Windows Update Service"
- In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile\AuthorizedApplications\List
- %System%\pidgen32.exe = "%System%\pidgen32.exe:*:Enabled:Windows Update Service"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer
- f0bdff95 = "{random values}"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Windows
- LoadAppInit_DLLs = "1"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\{57BEEE44-EE22-E631-FB0D-11C618C211B0}\InProcServer32
- ThreadingModel = "Apartment"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Browser Helper Objects\{57BEEE44-EE22-E631-FB0D-11C618C211B0}
- NoExplorer = "1"
Step 5
Restore this modified 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\Microsoft\Windows NT\CurrentVersion\Windows
- AppInit_Dlls = "%System%\strmfilt32.dll"
Step 6
Search and delete these files
- %System%\avtapi32.dll
- %System%\strmfilt32.dll
- %System%\020000004d8102a01270P.manifest
- %System%\020000004d8102a01270C.manifest
- %System%\020000004d8102a01270O.manifest
- %System%\020000004d8102a01270S.manifest
- %System%\msprivs32.exe
Step 7
Scan your computer with your Trend Micro product to delete files detected as TROJ_OBFUSCA.DCB. 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 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\Microsoft\Windows\CurrentVersion
- {B6FB50C5-70BB-4b1e-97E7-64B307776E8A}
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