Malware type: Backdoor

Aliases: No Alias Found

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:



A backdoor program is a Trojan specifically designed to allow malicious users to remotely manipulate affected systems. Like all Trojans, backdoors do not automatically propagate. They are either installed inadvertently by unsuspecting users or intentionally by malicious users.

Backdoors, like other Trojans, typically modify system settings to automatically start. Users may need to terminate backdoors before they can be deleted. Also, restoring affected systems may require procedures other than scanning with an antivirus program.

For additional information about this threat, see:

Description created: Jul. 27, 2009 4:10:28 PM GMT -0800


File type: PE

Memory resident:  Yes

Size of malware: 22,006 Bytes

Initial samples received on: Jul 21, 2009


Arrival Details

This backdoor may be dropped by other malware. It may be downloaded unknowingly by a user when visiting malicious Web site(s).


This backdoor drops the following copy(ies) of itself:

  • %System%\ms18_word.exe

(Note: %System% is the Windows system folder, which is usually C:\Windows\System on Windows 98 and ME, C:\WINNT\System32 on Windows NT and 2000, or C:\Windows\System32 on Windows XP and Server 2003.)

Autostart Techniques

This backdoor creates the following registry entry(ies) to enable its automatic execution at every system startup:

ms18_word = "%System%\ms18_word.exe"

ms18_word = "%System%\ms18_word.exe"

It runs the legitimate file SVCHOST.EXE and creates a remote thread to possibly access certain URLs to send and receive information.

Analysis By: Jasper Manuel

Revision History:

First pattern file version: 6.358.01
First pattern file release date: Aug 11, 2009


Minimum scan engine version needed: 8.700

Pattern file needed: 6.399.00

Pattern release date: Aug 26, 2009

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.


For Windows ME and XP users, before doing any scans, please make sure you disable System Restore to allow full scanning of your computer.

 Step 1: Identify and terminate files detected as BKDR_HAREBOT.W  [learn how]


  1. 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.
  2. 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.
  3. If the detected file is not displayed in either Windows Task Manager or Process Explorer, continue doing the next steps.

 Step 2:  Delete these registry values [learn how]

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.

  • In HKEY_CURRENT_USER\Software\Microsoft\
    • ms18_word = "%System%\ms18_word.exe"
  • In HKEY_LOCAL_MACHINE\Software\Microsoft\
    • ms18_word = "%System%\ms18_word.exe"

 Step 3: Scan your computer with your Trend Micro product to delete files detected as BKDR_HAREBOT.W

*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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