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 modifies the following registry entries to ensure it automatic execution at every system startup:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
Userinit = "%System%\userinit.exe,{malware path and file name},"
(Note: The default value data of the said registry entry is %Windows%\system32\userinit.exe,.)
Dropping Routine
This Trojan drops the following files:
- %User Startup%\nvvscv.exe
(Note: %User Startup% is the current user's Startup folder, which is usually C:\Windows\Profiles\{user name}\Start Menu\Programs\Startup on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Start Menu\Programs\Startup on Windows NT, and C:\Documents and Settings\{User name}\Start Menu\Programs\Startup.)
This report is generated via an automated analysis system.
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
Identify and delete files detected as TROJ_DROPPE.YYXL using either the Startup Disk or Recovery Console
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To identify and delete the malware/grayware file:
• On Windows XP and Server 2003 systems:
- Scan your computer with your Trend Micro product and then take note of the names of the malware/grayware files detected.
- Click Start>Run. In the Open input box, type secpol.msc and press Enter.
- In the left panel, double-click Local Policies>Security Options.
- In the right panel, double-click Recovery Console: Allow floppy copy and access to all drives and folders.
- Select Enabled and click OK.
- Insert the Windows Installation CD into the CD drive, then restart your computer.
- When prompted, press any key to boot from the CD.
- On the main menu, type r to go to the Recovery Console.
- Type the number that corresponds to the drive and directory that contains Windows (usually C:\WINDOWS) and press Enter.
- Type the Administrator password and press Enter.
- In the input box, type the following then press Enter:
SET AllowAllPaths = TRUE
del "{malware/grayware path and file name}" - Type exit and press Enter to restart the system normally.
• On Windows Vista and 7 systems:
- Scan your computer with your Trend Micro product and then take note of the names of the malware/grayware files detected.
- Insert your Windows Installation DVD in the DVD drive, then Press the restart button.
- When prompted, press any key to boot from the CD.
- Depending on your Windows Installation DVD, you might be required to select the installation language. Then on the Install Windows window, choose your language, locale, and keyboard layout or input method. Click Next, then click Repair your computer.
- Select Use recovery tools that can help fix problems starting Windows. Select your installation of Windows. Click Next.
- If the Startup Repair window appears, click Cancel, Yes, then Finish.
- In the System Recovery Options window, click Command Prompt.
- In the Command Prompt window, type the following then press Enter:
BootRec.exe /fixmbr
del "{malware/grayware path and file name}" - Type exit and press Enter to close the Command Prompt window.
- Click Restart to restart the system normally.
Step 3
Restore these modified registry values
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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\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
- From: Userinit = "%System%\userinit.exe,{malware path and file name},"
To: Userinit = ""%Windows%\system32\userinit.exe,""
To restore registry values this malware/grayware modified:
- Open Registry Editor. To do this:
- On Windows 2000, XP, and Server 2003:
Click Start>Run, type REGEDIT in the text box provided, and then press Enter. - On Windows Vista and 7:
Click the Start button, type REGEDIT in the Search input field then press Enter.
- In the left panel, double-click the following:
HKEY_LOCAL_MACHINE>SOFTWARE>Microsoft>Windows NT>CurrentVersion>Winlogon - In the right panel, locate the registry value:
Userinit = "%System%\userinit.exe,{malware path and file name}," - Right-click on the value name and choose Modify. Change the value data of this entry to:
Userinit = "%Windows%\system32\userinit.exe," - Close Registry Editor.
Step 4
Search and delete this file
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There may be some 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 Startup%\nvvscv.exe
To manually delete a malware/grayware file from an affected system:
• For Windows 2000, Windows XP, and Windows Server 2003:
- Right-click Start then click Search....
- In the left panel, click All Files.
- In the Named input box, type the following:
- %User Startup%\nvvscv.exe
- In the Look In drop-down list, select My Computer then press Enter.
- Once located, select the file then press SHIFT+DELETE to delete it.
• For Windows Vista and Windows 7 users:
- Click Start>Computer.
- In the Search input box, type the following:
- %User Startup%\nvvscv.exe
- Once located, select the file then press SHIFT+DELETE to delete it.
*Note: Read the following Microsoft page if these steps do not work on Windows 7.
Step 5
Scan your computer with your Trend Micro product to delete files detected as TROJ_DROPPE.YYXL. 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.
