Threat Encyclopedia

JS_WINDEXP.A

Malware type: JavaScript

Aliases: Download.Trojan, JS/Exploit-BO.gen

In the wild: Yes

Destructive: No

Language: English

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

Encrypted: Yes

Overall risk rating:

Reported infections:

Damage potential:

High

Distribution potential:

Medium

Description: 

This malicious JavaScript is downloaded on an affected system whenever the user accesses certain Web sites.

It takes advantage of the Windows buffer overflow vulnerability in Internet Explorer to remotely execute codes on an affected system. More information on this vulnerability can be found in the following Microsoft Web page:

Furthermore, this JavaScript downloads the indicated malware programs from the following sites:

  • http://afris.{BLOCKED}biz - KEKS.EXE detected by Trend Micro as TROJ_DLOADER.AUS
  • http://afris.{BLOCKED}biz/first - ALL.EXE detected by Trend Micro as TROJ_DELF.OP

For additional information about this threat, see:

Description created: Dec. 1, 2005 2:37:33 AM GMT -0800


TECHNICAL DETAILS


File type: Script

Size of malware: 2,726 Bytes

Initial samples received on: Nov 29, 2005

Vulnerability used:  (MS05-054) Cumulative Security Update for Internet Explorer (905915)

Related toTROJ_DLOADER.AUS, TROJ_DELF.OP

Payload 1: Downloads other malware

Payload 2: Takes advantage of Windows vulnerability

Details:

This malicious JavaScript is downloaded on an affected system whenever the user accesses the following Web sites:

  • http://afris.biz{BLOCKED}/poc/fillmem.htm
  • http://afris.biz{BLOCKED}/poc/sp4.htm

It takes advantage of the Windows buffer overflow vulnerability in Internet Explorer to remotely execute codes on an affected system. More information on this vulnerability can be found in the following Microsoft Web page:

Furthermore, this JavaScript downloads the indicated malware programs from the following sites:

  • http://afris.{BLOCKED}biz - KEKS.EXE detected by Trend Micro as TROJ_DLOADER.AUS
  • http://afris.{BLOCKED}biz/first - ALL.EXE detected by Trend Micro as TROJ_DELF.OP

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

Analysis By: Jocelyn D. Racoma

Revision History:

 

Dec 20, 2005 � Insertion of reference to Microsoft Security Bulletin MS05-054

SOLUTION


Minimum scan engine version needed: 7.000

Pattern file needed: 2.978.02

Pattern release date: Dec 1, 2005


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:

Important Windows ME/XP Cleaning Instructions

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

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

Running Trend Micro Antivirus

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

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

Applying Patches

This malware exploits known vulnerabilities in Internet Explorer. Download and install the fix patch supplied by Microsoft. Refrain from using this product until the appropriate patch has been installed. Trend Micro advises users to download critical patches upon release by vendors.




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