WORM_GAMARUE.DA

 Analysis by: Rhena Inocencio

 ALIASES:

Worm:Win32/Gamarue.I (Microsoft), W32/Andromeda.UCG!tr.dldr (Fortinet), a variant of Win32/Injector.AEYF trojan (Nod32)

 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:

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Dropped by other malware, Downloaded from the Internet, Propagates via removable drives

This Trojan may be downloaded by other malware/grayware from remote sites. It may be dropped by other malware.

It executes commands from a remote malicious user, effectively compromising the affected system. It connects to a website to send and receive information.

It executes the dropped file(s). As a result, malicious routines of the dropped files are exhibited on the affected system.

  TECHNICAL DETAILS

File Size:

840,192 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

10 Apr 2013

Payload:

Connects to URLs/IPs, Downloads files, Drops files

Arrival Details

This Trojan may be downloaded by the following malware/grayware from remote sites:

  • http://{BLOCKED}r.dl.{BLOCKED}forge.net/project/stubpe/a/zwz - (encrypted copy)

It may be dropped by the following malware:

Installation

This Trojan creates the following folders:

  • %User Temp%\_install_

(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 injects codes into the following process(es):

  • wuauclt.exe

Autostart Technique

This Trojan adds the following registry entries to enable its automatic execution at every system startup:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\policies\
Explorer\Run
{random number} = "%All Users Profile%\Temp\ms{random}.{extension}"

Other System Modifications

This Trojan modifies the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
Hidden = "2"

(Note: The default value data of the said registry entry is 1.)

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
ShowSuperHidden = "0"

(Note: The default value data of the said registry entry is 1.)

Backdoor Routine

This Trojan executes the following commands from a remote malicious user:

  • Download a file from C&C server and save it as %User Temp%\{random number}.exe
  • Download a file from C&C server and save it as %System Root%\Documents and Settings\All Users\ms{random number}.dat and loads it
  • Start a process
  • Uninstall itself
  • Remote command prompt

(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.. %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.)

It connects to the following websites to send and receive information:

  • http://{BLOCKED}cgrvkj.ru/in.php
  • http://{BLOCKED}tvmein.in/in.php
  • http://{BLOCKED}wsqhct.in/in.php
  • http://{BLOCKED}onzmwuehky.nl/in.php
  • http://{BLOCKED}ososoft.ru/in.php

Dropping Routine

This Trojan drops the following files:

  • %All Users Profile%\Local Settings\Temp\ms{random}.{extension}
  • %User Temp%\_install_\msiexec.exe

(Note: %All Users Profile% is the All Users or Common profile folder, which is C:\Documents and Settings\All Users in Windows 2000, XP, and Server 2003, and C:\ProgramData in Windows Vista and 7.. %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 executes the dropped file(s). As a result, malicious routines of the dropped files are exhibited on the affected system.

NOTES:

The {extension} of the dropped file can be any of the following:

  • BAT
  • CMD
  • COM
  • EXE
  • PIF
  • SCR

It propagates by dropping the following component files in removable drives:

  • {drive name} ({drive size}).LNK - LNK_GAMARUE.DA
  • ~${random}.{diskformat} - TROJ_GAMARUE.DA
  • desktop.ini - TROJ_GAMARUE.SM

It copies all the user's folders and files in the removable drive into a hidden folder with name of ASCII 255, which is displayed as a special space character.

It sets the attribute of all files and folders in removable drives to Hidden.

It checks if it is being run in VMWare environment.

  SOLUTION

Minimum Scan Engine:

9.300

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 the malware/grayware file dropped/downloaded by WORM_GAMARUE.DA

     
    • TROJ_GAMARUE.SM
    • LNK_GAMARUE.DA
    • TROJ_GAMARUE.DA

Step 3

Restart in Safe Mode

[ Learn More ]

Step 4

Delete this 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\Explorer\Run
    • {random number} = "%All Users Profile%\Temp\ms{random}.{extension}"

Step 5

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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
    • From: Hidden = "2"
      To: Hidden = "1"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
    • From: ShowSuperHidden = "0"
      To: ShowSuperHidden = "1"

Step 6

Search and delete this folder

[ Learn More ]
Please make sure you check the Search Hidden Files and Folders checkbox in the More advanced options option to include all hidden folders in the search result.
  • %User Temp%\_install_

Step 7

Search and delete this file

[ 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.
  • %All Users Profile%\Local Settings\Temp\ms{random}.{extension}

Step 8

Restart in normal mode and scan your computer with your Trend Micro product for files detected as WORM_GAMARUE.DA. 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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