Threat Encyclopedia


Malware type: JavaScript

Aliases: (Kaspersky), JS/Downloader-AUD (McAfee), Downloader (Symantec), JS/Dldr.IESli (Avira), Mal/ExpJS-D (Sophos), Exploit:JS/Mult.K (Microsoft)

In the wild: Yes

Destructive: No

Language: English

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

Encrypted: No

Overall risk rating:

Reported infections:

Damage potential:


Distribution potential:



To get a one-glance comprehensive view of the behavior of this malware, refer to the Behavior Diagram shown below.

JS_IESLICE.AQ Behavior Diagram

Malware Overview

This malicious JavaScript is hosted on a Web site and run when a user accesses the said Web site.

It accesses Web sites to download files. As a result, malicious routines of the downloaded files may be exhibited on the affected system.

It takes advantage of software vulnerabilities, which allows a remote malicious user or malware to download files on the affected machine. It saves the downloaded files using certain file names.

For additional information about this threat, see:

Description created: Jan. 12, 2008 1:00:05 AM GMT -0800


File type: Script

Size of malware: 31,535 Bytes

Initial samples received on: Jan 12, 2008

Payload 1: Downloads files


Arrival Details

This malicious JavaScript is hosted on a Web site and run when a user accesses the said Web site.

Download Routine

This malicious JavaScript accesses the following URL to download files:

  • http://{host site}/{8 random characters}

(Note: {host site} refers to the domain being compromised.)

It takes advantage of the following software vulnerabilities:

Upon successful exploit, the system is redirected to the following Web site to download a malicious file detected as a variant of XML_HACK:

  • http://{BLOCKED}

It saves the downloaded files as the following:

  • C:\mosvs8.exe
  • C:\win{random 4 characters}.exe

It then executes the downloaded files. As a result, malicious routines of the downloaded files are exhibited on the affected system.

Affected Platforms

This malicious JavaScript runs on Windows 98, ME, NT, 2000, XP, and Server 2003.

Analysis By: Christian Fajutagana

Revision History:

First pattern file version: 4.942.29
First pattern file release date: Jan 12, 2008


Minimum scan engine version needed: 8.300

Pattern file needed: 4.949.00

Pattern release date: Jan 16, 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.


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

Terminating the Malware Process

The succeeding procedures require that the following processes be terminated. This step terminates related running malware processes.

  1. Open Windows Task Manager.
    • On Windows 98 and ME, press
    • 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 process:
  3. Select the malware process, then press either the End Task or the End Process button, depending on the version of Windows on your computer.
  4. To check if the malware process has been terminated, close Task Manager, and then open it again.
  5. Repeat steps 2-4 for the following process:
    win{Random 4 characters}.exe
    (Note the {Random 4 characters} used in the string.)
  6. Close Task Manager.

*NOTE: On computers running Windows 98 and ME, Windows Task Manager may not show certain processes. You can use a third party process viewer such as Process Explorer to terminate the malware process.

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. 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.

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:
  3. In the Look In drop-down list, select My Computer, then press Enter.
  4. Once located, select the file then press SHIFT+DELETE.
  5. Repeat steps 2 to 4 to delete the following file:
    C:\win{Random 4 characters}.exe
    (Note: Use the {Random 4 characters} noted in the process terminated earlier.)

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 JS_IESLICE.AQ. To do this, Trend Micro customers must download the latest virus pattern file and scan their computers. Other Internet users can use HouseCall, the Trend Micro online threat scanner.

Applying Patches

Download and install the following patches:

Refrain from using these products until the appropriate patches have been installed. Trend Micro advises users to download critical patches upon release by vendors.

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

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