This memory-resident Trojan arrives as a dropped or downloaded file by other malware. It may also be downloaded and manually installed by an unsuspecting user from the Internet.

When executed, it drops its component .DLL file, which it registers as a Browser Helper Object (BHO), enabling the said file to execute whenever an instance of Internet Explorer (IE) is executed. Trend Micro also detects the .DLL as TROJ_LINKOPTIM.V.

This Trojan is also capable of downloading a malicious file from a certain URL and saving it in the Windows folder. Trend Micro detects the downloaded file as TROJ_AGENT.ESB.

TROJ_LINKOPTIM.V remains memory-resident until the affected system is disconnected from the Internet. It also terminates itself after it performs its download routine.

Solution:

(Note: Close all instances of Internet Explorer before proceeding with the solution below.)

Identifying the Malware Program

To remove this malware, first identify the malware program.

1. Scan your computer with your Trend Micro antivirus product.
2. NOTE the path and file name of all files detected as TROJ_LINKOPTIM.V.

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

Terminating the Malware Program

This procedure terminates the running malware process. You will need the name(s) of the file(s) detected earlier.

If the process you are looking for is not in the list displayed by Task Manager, proceed to the succeeding solution set.

1. Open Windows Task Manager.
   • On Windows 98 and ME, press
   CTRL+ALT+DELETE
   • On Windows NT, 2000, XP, and Server 2003, press
   CTRL+SHIFT+ESC, then click the Processes tab.
2. In the list of running programs*, locate the malware file(s) detected earlier.
3. Select one of the detected files, then press either the End Task or the End Process button, depending on the version of Windows on your computer.
4. Do the same for all detected malware files in the list of running processes.
5. To check if the malware process has been terminated, close Task Manager, and then open it again.
6. Close Task Manager.

On computers running all Windows platforms, if the process you are looking for is not in the list displayed by Task Manager or Process Explorer, continue with the next solution procedure, noting additional instructions. If the malware process is in the list displayed by either Task Manager or Process Explorer, but you are unable to terminate it, restart your computer in safe mode.

Editing the Registry

This malware modifies the computer's registry. Users affected by this malware may need to modify or delete specific registry keys or entries. For detailed information regarding registry editing, please refer to the following articles from Microsoft:

1. HOW TO: Backup, Edit, and Restore the Registry in Windows 95, Windows 98, and Windows ME
2. HOW TO: Backup, Edit, and Restore the Registry in Windows NT 4.0
3. HOW TO: Backup, Edit, and Restore the Registry in Windows 2000
4. HOW TO: Back Up, Edit, and Restore the Registry in Windows XP and Server 2003

Removing Added Key from the Registry

If the registry key below is not found, the malware may not have executed as of detection. If so, proceed to the succeeding solution set.

1. Open Registry Editor. Click Start>Run, type REGEDIT, then press Enter.
2. In the left panel, double-click the following:
   HKEY_LOCAL_MACHINE>SOFTWARE>Classes>CLSID
3. Again in the left panel, locate and delete the key:
   {391a72a1-108d-435a-875e-5b9048e11657}
4. Close Registry Editor.

(Note: Restart your computer before proceeding with the following solution.)

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

If you are currently running in safe mode, please restart your computer normally before performing the following solution.

Scan your computer with Trend Micro antivirus and delete files detected as TROJ_LINKOPTIM.V and TROJ_AGENT.ESB. To do this, Trend Micro customers must download the latest virus pattern file and scan their computer.