Minimum scan engine version needed: 8.300

Pattern file needed: 5.205.00

Pattern release date: Apr 7, 2008

Important note: The "Minimum scan engine" refers to the earliest Trend Micro scan engine version guaranteed to detect this threat. However, Trend Micro strongly recommends that you update to the latest version in order to get comprehensive protection. Download the latest scan engine here.

Solution:

Note: To fully remove all associated malware, perform the clean solutions for the following:

• MAL_OTORUN2
• WORM_IMAUT.Q

Identifying the Malware Files

1. Scan your computer with your Trend Micro antivirus product.
2. Note the path and file name of all files detected as WORM_IMAUT.AA.

Trend Micro customers need to download the latest virus pattern file before scanning their computer. Other users can use Housecall, the Trend Micro online threat scanner.

Terminating the Malware Program

Since this malware terminates the Windows Task Manager, it is necessary to use third party process viewers such as Process Explorer. You will need the name(s) of the file(s) detected earlier.

1. Download Process Explorer.
2. Extract the contents of the compressed (ZIP) file to a location of your choice.
3. Execute Process Explorer by double-clicking procexp.exe.
4. In the Process Explorer window, locate the malware file(s) detected earlier.
5. Right-click one of the detected files, then click Kill Process Tree.
6. Do the same for all detected malware files in the list of running processes.
7. Close Process Explorer.

Enabling The Registry Editor

This malware disables the Registry Editor. To restore the said system tool, perform the following instructions:

1. Open Notepad. Click Start>Run, type Notepad, then press Enter.
2. Copy and paste the following:
   REGEDIT4 [HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\System] "DisableRegistryTools" = dword:00000000
3. Save this file as C:\RESTORE.REG.
4. Click Start>Run, type C:\RESTORE.REG, then press Enter.
5. Click Yes at the prompt of the message box.

1. Open the Run dialog box. Click Start>Run, type Notepad, then press Enter.
2. Copy and paste the following:
   REG add HKCU\Software\Microsoft\Windows\CurrentVersion\Policies\System /v DisableRegistryTools /t REG_DWORD /d 0 /f
3. Save this file as C:\RESTORE.REG.
4. Click Start>Run, type C:\RESTORE.REG, then press Enter.
5. Click Yes at the prompt of the message box.

Removing Autostart Entries from the Registry

This solution deletes/modifies registry keys/entries added/modified by this malware. Before performing the steps below, make sure you know how to back up the registry and how to restore it if a problem occurs. Refer to this Microsoft article for more information about modifying your computer's registry.

1. Open Registry Editor. Click Start>Run, type REGEDIT, then press Enter.
2. In the left panel, double-click the following:
   HKEY_CURRENT_USER>Software>Microsoft>Windows>
   CurrentVersion>Run
3. In the right panel, locate and delete the entry:
   Yahoo Messengger = "%system%\regsvr.exe"
   

Restoring Modified Registry Entries

1. In the left panel, double-click the following:
   HKEY_LOCAL_MACHINE>SOFTWARE>Microsoft>Windows NT> CurrentVersion>Winlogon
2. In the right panel, locate the entry:
   Shell = "Explorer.exe" "Explorer.exe rundll.exe""
3. Right-click on the value name and choose Modify. Change the value data of this entry to:
   Explorer.exe
4. In the left panel, double-click the following:
   HKEY_LOCAL_MACHINE>SOFTWARE>Microsoft>Windows NT> CurrentVersion>Winlogon
5. In the right panel, locate the entry:
   System = "Winhelp.exe"
6. Right-click on the value name and choose Modify. Delete the value data of this entry.

Removing Other Malware Entries from the Registry

1. In the left panel, double-click the following:
   HKEY_CURRENT_USER>Software>Microsoft>Windows> CurrentVersion>Policies>System
2. In the right panel, locate and delete the entry:
   DisableRegistryTools = "1"
   DisableTaskMgr = "0"
3. In the left panel, double-click the following:
   HKEY_CURRENT_USER>Software>Microsoft>Windows> CurrentVersion>Policies>Explorer
4. In the right panel, locate and delete the entry:
   NofolderOptions = "0"
5. Close Registry Editor.

Deleting the Malware File(s)

1. Right-click Start then click Search... or Find..., depending on the version of Windows you are running.
2. In the Named input box, type:
   %System%\setup.ini
3. In the Look In drop-down list, select the drive that contains Windows, then press Enter.
4. Once located, select the file then press SHIFT+DELETE.

Deleting Malware-created AUTORUN.INF/s

1. Right-click Start then click Search... or Find..., depending on the version of Windows you are running.
2. In the Named input box, type:
   AUTORUN.INF
3. In the Look In drop-down list, select a drive, then press Enter.
4. Select the file, then open using Notepad.
5. Check if the following lines are present in the file:
   Open=regsvr.exe
   Shellexecute=regsvr.exe
   Shell\Open\Command=regsvr.exe
   Shell=Open
6. If the lines are present, delete the file.
7. Repeat steps 3 to 6 for AUTORUN.INF files in the remaining removable drives.
8. Close Search Results.

Important Windows ME/XP Cleaning Instructions

Users running Windows ME and XP must disable System Restore to allow full scanning of infected computers.

Users running other Windows versions can proceed with the succeeding solution set(s).

Running Trend Micro Antivirus

Scan your computer with Trend Micro antivirus and delete files detected as WORM_IMAUT.AA. To do this, Trend Micro customers must download the latest virus pattern file and scan their computer. Other Internet users can use HouseCall, the Trend Micro online virus scanner.

Trend Micro offers best-of-breed antivirus and content-security solutions for your corporate network, small and medium business, mobile device or home PC.

For additional information about this threat, see:
Overview
Technical Details

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