Analysis by:


Windows 98, ME, NT, 2000, XP, Server 2003


  • Threat Type:

  • Destructiveness:

  • Encrypted:

  • In the wild: Yes


This Backdoor adds registry entries to enable its automatic execution at every system startup.


File Size: 155648 bytes
Initial Samples Received Date: 05 Apr 2010


This Backdoor drops the following files:

    • %System%\MSCONFIG32.SYS
    • %System%\~msw0.tmp
    • %Program Files%\Java\jre6\bin\zf32.dll

(Note: %Program Files% is the default Program Files folder, usually C:\Program Files.)

Autostart Technique

This Backdoor adds the following registry entries to enable its automatic execution at every system startup:

It drops the following files:

    • %User Startup%\jucheck.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.)


Step 1

Terminate the malware/grayware/spyware process:

[ Learn More ]
  • For Windows 98 and ME users, Windows Task Manager may not display all running processes. In this case, please use a third-party process viewer, preferably Process Explorer, to terminate the malware/grayware/spyware file. You may download the said tool here.
  • If the detected file is displayed in either Windows Task Manager or Process Explorer but you cannot delete it, restart your computer in safe mode. To do this, refer to this link for the complete steps.
  • If the detected file is not displayed in either Windows Task Manager or Process Explorer, continue doing the next steps.

  • Step 2

    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.

      • %Application Data%\Java\jre6\bin\jucheck.exe=REG_SZ

    Step 3

    Search and delete these files

    [ Learn More ]
    There may be some component 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%\jucheck.exe
    • %System%\MSCONFIG32.SYS
    • %System%\~msw0.tmp
    • %Program Files%\Java\jre6\bin\zf32.dll

    Note: To do a search for the following files, right-click Start then click Search... or Find..., depending on the version of Windows you are running. For each file to be deleted, type its file name in the Named input box. In the Look In drop-down list, select My Computer, then press Enter.
  • Once located, select the file then press SHIFT+DELETE to permanently delete the file.
  • Repeat the said steps for all files listed.

  • Step 4

    Restore this file from backup Only Microsoft-related files will be restored. If this malware/grayware/spyware also deleted files related to programs that are not from Microsoft, please reinstall those programs on your computer again.

    • %Program Files%\Java\jre6\bin\jucheck.exe
    • %Application Data%\Java\jre6\bin\zf32.dll
    • %Application Data%\Java\jre6\bin\jucheck.exe

    Step 5

    Scan your computer with your Trend Micro product to delete files detected as

    *Note: 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.

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