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JS_DOWNCRYPT.A

September 06, 2014
 Analysis by: Rhena Inocencio
 ALIASES:

Trojan-Downloader.JS.Scatter.a (Kaspersky)

 PLATFORM:

Windows 2000, Windows Server 2003, Windows XP (32-bit, 64-bit), Windows Vista (32-bit, 64-bit), Windows 7 (32-bit, 64-bit)

 OVERALL RISK RATING:
 DAMAGE POTENTIAL:
 DISTRIBUTION POTENTIAL:
 REPORTED INFECTION:
 INFORMATION EXPOSURE:

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Via email


This Trojan arrives as an attachment to email messages spammed by other malware/grayware or malicious users.

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

  TECHNICAL DETAILS

File Size:

Varies

File Type:

JS

Memory Resident:

No

Initial Samples Received Date:

01 Sep 2014

Payload:

Downloads files

Arrival Details

This Trojan arrives as an attachment to email messages spammed by other malware/grayware or malicious users.

Download Routine

This Trojan accesses the following websites to download files:

  • http://{BLOCKED}u.org/images/document.btc
  • http://{BLOCKED}u.org/images/day.btc
  • http://{BLOCKED}u.org/images/null.btc
  • http://{BLOCKED}u.org/images/keybtc.btc
  • http://{BLOCKED}u.org/images/sad.btc

It saves the files it downloads using the following names:

  • %User Temp%\docu.doc - non-malicious. decoy document
  • %User Temp%\keybtc.bat - detected as BAT_CRYPTOR.B
  • %User Temp%\day.btc
  • %User Temp%\null.btc
  • %User Temp%\sad.btc

(Note: %User Temp% is the current user's Temp folder, which is usually C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Local\Temp on Windows Vista and 7.)

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

  SOLUTION

Minimum Scan Engine:

9.700

FIRST VSAPI PATTERN FILE:

11.132.01

FIRST VSAPI PATTERN DATE:

06 Sep 2014

VSAPI OPR PATTERN File:

11.133.00

VSAPI OPR PATTERN Date:

07 Sep 2014

Step 1

Before doing any scans, Windows XP, Windows Vista, and Windows 7 users must disable System Restore to allow full scanning of their computers.

Step 2

Note that not all files, folders, and registry keys and entries are installed on your computer during this malware's/spyware's/grayware's execution. This may be due to incomplete installation or other operating system conditions. If you do not find the same files/folders/registry information, please proceed to the next step.

Step 3

Remove malware/grayware files dropped/downloaded by JS_DOWNCRYPT.A. (Note: Please skip this step if the threats listed below have already been removed.)

    • BAT_CRYPTOR.B

Step 4

Search and delete these files

[ Learn More ]
There may be some files that are hidden. Please make sure you check the Search Hidden Files and Folders checkbox in the "More advanced options" option to include all hidden files and folders in the search result.  
  • %User Temp%\day.btc
  • %User Temp%\null.btc
  • %User Temp%\sad.btc
  • %User Temp%\docu.doc

Step 5

Scan your computer with your Trend Micro product to delete files detected as JS_DOWNCRYPT.A. 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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