Analysis by: Francis Xavier Antazo
ALIASES:

a variant of Win32/TrojanDownloader.Autoit.NWP trojan (NOD32)

 PLATFORM:

Windows

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

  • Threat Type: Worm

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

This worm arrives via removable drives. It arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It uses the default Windows folder icon to trick users into opening the file. Double-clicking the file executes this malware.

It drops copies of itself into network drives.

  TECHNICAL DETAILS

File Size: 458,752 bytes
File Type: EXE
Memory Resident: No
Initial Samples Received Date: 11 Jan 2015

Arrival Details

This worm arrives via removable drives.

It arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

Installation

This worm uses the default Windows folder icon to trick users into opening the file. Double-clicking the file executes this malware.

Other System Modifications

This worm modifies the following registry entries:

HKEY_LOCAL_MACHINE\Software\Microsoft\
Windows\CurrentVersion\Policies\
System
ConsentPromptBehaviorAdmin = "0"

(Note: The default value data of the said registry entry is "5".)

Propagation

This worm drops the following copies of itself in all physical and removable drives:

  • {drive letter}:\{original folder name}.exe

It drops copies of itself into network drives.

Download Routine

This worm connects to the following website(s) to download and execute a malicious file:

  • {BLOCKED}videos.xyz/ext/go.exe (detected as TROJ64_EXTENBRO.AJ)

It saves the files it downloads using the following names:

  • %Application Data%\svchosts.exe ( detected as TROJ64_EXTENBRO.AJ )

(Note: %Application Data% is the Application Data folder, where it usually is C:\Documents and Settings\{user name}\Application Data on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Roaming on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.)

NOTES:

It tries to copy itself to mounted CD drives.

It hides the folders on the drives that it infects and disguises its copies as the original folder.

It connects to the following URLs to download non-malicious files

  • http://whos.{BLOCKED}ng.us/small/00/{random digits}.png

  SOLUTION

Minimum Scan Engine: 9.700
FIRST VSAPI PATTERN FILE: 11.408.01
FIRST VSAPI PATTERN DATE: 11 Jan 2015
VSAPI OPR PATTERN File: 11.409.00
VSAPI OPR PATTERN Date: 12 Jan 2015

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

Remove malware/grayware files dropped/downloaded by WORM64_FOLDLER.A. (Note: Please skip this step if the threats listed below have already been removed.)

     
    • TROJ64_EXTENBRO.AJ

Step 3

Restore this modified registry value

[ Learn More ]

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_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Policies\System
    • From: ConsentPromptBehaviorAdmin = "0"
      To: ConsentPromptBehaviorAdmin = "5"

Step 4

Scan your computer with your Trend Micro product to delete files detected as WORM64_FOLDLER.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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