TROJ_THORSE.A
Adware:Win32/CenturyHerosoft, TrojanDownloader:Win32/Small.gen!F (Microsoft); [2.nsis]:Generic PUP.g., [3.nsis]:generic!bg.eyo (McAfee); Suspicious.MH690 (Symantec); ARC:NSIS, ARC:[setup10.exe]:NSIS, PAK:[103172.exe]:UPX (Kaspersky); Trojan-Downloader.Win32.Small (Sunbelt); Trojan.Downloader.Small.F (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 creates the following folders:
- %System Root%\DOCUME~1
- %System Root%\DOCUME~1\ADMINI~1
- %User Profile%\LOCALS~1
(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:\Windows\Profiles\{user name} on Windows 98 and ME, C:\WINNT\Profiles\{user name} on Windows NT, and C:\Documents and Settings\{user name} on Windows 2000, 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\{721E6521-4CAD-4A8D-A7F1-4E230B31EF19}
It registers as a system service to ensure its automatic execution at every system startup by adding the following registry keys:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile\AuthorizedApplica
Other System Modifications
This Trojan deletes the following files:
- %User Temp%\nsr1.tmp
- %User Temp%\nsi3.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.)
It adds the following registry keys:
HKEY_LOCAL_MACHINE\SOFTWARE\dmshareware
HKEY_CLASSES_ROOT\MSHLP.MSHlper.1
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
MSHLP.MSHlper.1\CLSID
HKEY_CLASSES_ROOT\MSHLP.MSHlper
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
MSHLP.MSHlper\CLSID
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
MSHLP.MSHlper\CurVer
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{721E6521-4CAD-4A8D-A7F1-4E230B31EF19}
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{721E6521-4CAD-4A8D-A7F1-4E230B31EF19}\ProgID
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{721E6521-4CAD-4A8D-A7F1-4E230B31EF19}\VersionIndependentProgID
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{721E6521-4CAD-4A8D-A7F1-4E230B31EF19}\Programmable
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{721E6521-4CAD-4A8D-A7F1-4E230B31EF19}\InprocServer32
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{721E6521-4CAD-4A8D-A7F1-4E230B31EF19}\TypeLib
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Explorer\
Browser Helper Objects
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
TypeLib\{203B711D-08CE-47B4-9A22-C99A4C22224C}
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
TypeLib\{203B711D-08CE-47B4-9A22-C99A4C22224C}\1.0
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
TypeLib\{203B711D-08CE-47B4-9A22-C99A4C22224C}\1.0\
FLAGS
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
TypeLib\{203B711D-08CE-47B4-9A22-C99A4C22224C}\1.0\
0
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
TypeLib\{203B711D-08CE-47B4-9A22-C99A4C22224C}\1.0\
0\win32
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
TypeLib\{203B711D-08CE-47B4-9A22-C99A4C22224C}\1.0\
HELPDIR
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Interface\{A6A82A97-8EB8-495A-AE49-1912793FE4EC}
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Interface\{A6A82A97-8EB8-495A-AE49-1912793FE4EC}\ProxyStubClsid
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Interface\{A6A82A97-8EB8-495A-AE49-1912793FE4EC}\ProxyStubClsid32
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Interface\{A6A82A97-8EB8-495A-AE49-1912793FE4EC}\TypeLib
It adds the following registry entries:
HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\SharedAccess\Parameters\
FirewallPolicy\StandardProfile\AuthorizedApplications\
List
%User Temp%\103172.exe = "%User Temp%\103172.exe:*:Enabled:DM"
HKEY_LOCAL_MACHINE\SOFTWARE\dmshareware
Owner = "103172"
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
CLSID\{721E6521-4CAD-4A8D-A7F1-4E230B31EF19}\InprocServer32
ThreadingModel = "Apartment"
HKEY_LOCAL_MACHINE\SOFTWARE\Classes\
Interface\{A6A82A97-8EB8-495A-AE49-1912793FE4EC}\TypeLib
Version = "1.0"
Dropping Routine
This Trojan drops the following files:
- %User Temp%\nsr2.tmp
- %User Temp%\setup10.exe
- %User Temp%\103172.exe
- %User Temp%\nsy4.tmp
- %System%\mscfg.ini
- %System%\MSHLP.DLL
- %Windows%\Tasks\DM_Install_Program.job
- %Temp%\ie.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.. %Temp% is the Windows Temporary folder, which is usually C:\Windows\Temp or C:\WINNT\Temp.)
Other Details
This Trojan connects to the following possibly malicious URL:
- http://ulink4.{BLOCKED}u.com/setup/iebar.exe
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
Restart in Safe Mode
Step 3
Close all opened browser windows
Step 4
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_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SharedAccess\Parameters\FirewallPolicy\StandardProfile
- AuthorizedApplica
- In HKEY_LOCAL_MACHINE\SOFTWARE
- dmshareware
- In HKEY_CLASSES_ROOT
- MSHLP.MSHlper.1
- In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\MSHLP.MSHlper.1
- CLSID
- In HKEY_CLASSES_ROOT
- MSHLP.MSHlper
- In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\MSHLP.MSHlper
- CLSID
- In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\MSHLP.MSHlper
- CurVer
- In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID
- {721E6521-4CAD-4A8D-A7F1-4E230B31EF19}
- In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\{721E6521-4CAD-4A8D-A7F1-4E230B31EF19}
- ProgID
- In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\{721E6521-4CAD-4A8D-A7F1-4E230B31EF19}
- VersionIndependentProgID
- In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\{721E6521-4CAD-4A8D-A7F1-4E230B31EF19}
- Programmable
- In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\{721E6521-4CAD-4A8D-A7F1-4E230B31EF19}
- InprocServer32
- In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\{721E6521-4CAD-4A8D-A7F1-4E230B31EF19}
- TypeLib
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer
- Browser Helper Objects
- In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\TypeLib
- {203B711D-08CE-47B4-9A22-C99A4C22224C}
- In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\TypeLib\{203B711D-08CE-47B4-9A22-C99A4C22224C}
- 1.0
- In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\TypeLib\{203B711D-08CE-47B4-9A22-C99A4C22224C}\1.0
- FLAGS
- In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\TypeLib\{203B711D-08CE-47B4-9A22-C99A4C22224C}\1.0
- 0
- In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\TypeLib\{203B711D-08CE-47B4-9A22-C99A4C22224C}\1.0\0
- win32
- In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\TypeLib\{203B711D-08CE-47B4-9A22-C99A4C22224C}\1.0
- HELPDIR
- In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Interface
- {A6A82A97-8EB8-495A-AE49-1912793FE4EC}
- In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Interface\{A6A82A97-8EB8-495A-AE49-1912793FE4EC}
- ProxyStubClsid
- In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Interface\{A6A82A97-8EB8-495A-AE49-1912793FE4EC}
- ProxyStubClsid32
- In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Interface\{A6A82A97-8EB8-495A-AE49-1912793FE4EC}
- TypeLib
Step 5
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\StandardProfile\AuthorizedApplications\List
- %User Temp%\103172.exe = "%User Temp%\103172.exe:*:Enabled:DM"
- In HKEY_LOCAL_MACHINE\SOFTWARE\dmshareware
- Owner = "103172"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID\{721E6521-4CAD-4A8D-A7F1-4E230B31EF19}\InprocServer32
- ThreadingModel = "Apartment"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Interface\{A6A82A97-8EB8-495A-AE49-1912793FE4EC}\TypeLib
- Version = "1.0"
Step 6
Search and delete these files
- %User Temp%\nsr2.tmp
- %User Temp%\setup10.exe
- %User Temp%\103172.exe
- %User Temp%\nsy4.tmp
- %System%\mscfg.ini
- %System%\MSHLP.DLL
- %Windows%\Tasks\DM_Install_Program.job
- %Temp%\ie.exe
Step 7
Search and delete these folders
- %System Root%\DOCUME~1
- %System Root%\DOCUME~1\ADMINI~1
- %User Profile%\LOCALS~1
Step 8
Restart in normal mode and scan your computer with your Trend Micro product for files detected as TROJ_THORSE.A. 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 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%\nsr1.tmp
- %User Temp%\nsi3.tmp
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