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TROJ_REMTASU.LN

March 29, 2014
 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW


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

It disables Task Manager, Registry Editor, and Folder Options.

  TECHNICAL DETAILS

File Size:

1,123,900 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

25 Mar 2014

Arrival Details

This Trojan 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 Trojan creates the following folders:

  • %System Root%\Documents and Settings\Wilbert
  • %User Profile%\kc1939z1z477
  • %User Profile%\Windows\HAnXQouasfo
  • %Windows%\WinDir

(Note: %System Root% is the root folder, which is usually C:\. It is also where the operating system is located.. %User Profile% is the current user's profile folder, which is usually C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003, or C:\Users\{user name} on Windows Vista and 7.. %Windows% is the Windows folder, which is usually C:\Windows.)

Autostart Technique

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\RunOnce
kc1939z1z477 = "%User Profile%\kc1939z1z477\56846.vbs"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
HKLM = "%Windows%\WinDir\Server.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
HKCU = "%Windows%\WinDir\Server.exe"

Other System Modifications

This Trojan adds the following registry keys:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\RunOnce

HKEY_CURRENT_USER\SOFTWARE\HAnXQouasfo

It adds the following registry entries:

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

HKEY_CURRENT_USER\Software\HAnXQouasfo
ServerStarted = "3/18/2014 14:55:16 PM"

HKEY_CURRENT_USER\Software\HAnXQouasfo
InstalledServer = "%Windows%\WinDir\Server.exe"

It creates the following registry entry(ies) to disable Task Manager, Registry Tools and Folder Options:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
Explorer
NoFolderOptions = "1"

Dropping Routine

This Trojan drops the following files:

  • __tmp_rar_sfx_access_check_149796
  • uRgBTn.SII
  • UXpCwuTvSZ.exe
  • lJwwOuSYyRXG.GRB
  • rYpFHPKAy.PBM
  • %User Profile%\HAnXQouasfo\HAnXQouasfo.nfo
  • %User Temp%\x.html
  • %User Profile%\HAnXQouasfo\HAnXQouasfo.svr
  • %Windows%\WinDir\Server.exe

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

This report is generated via an automated analysis system.

  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

Restart in Safe Mode

[ Learn More ]

Step 3

Enable Registry Editor, Task Manager, and Folder options

[ Learn More ]
By doing this step, you also enable other applications/programs disabled by this malware/grayware/spyware.

Step 4

Delete this registry key

[ 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
    • RunOnce
  • In HKEY_CURRENT_USER\SOFTWARE
    • HAnXQouasfo

Step 5

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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\RunOnce
    • kc1939z1z477 = "%User Profile%\kc1939z1z477\56846.vbs"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • HKLM = "%Windows%\WinDir\Server.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • HKCU = "%Windows%\WinDir\Server.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
    • ShowSuperHidden = "0"
  • In HKEY_CURRENT_USER\Software\HAnXQouasfo
    • ServerStarted = "3/18/2014 14:55:16 PM"
  • In HKEY_CURRENT_USER\Software\HAnXQouasfo
    • InstalledServer = "%Windows%\WinDir\Server.exe"

Step 6

Search and delete these components

[ Learn More ]
There may be some components 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.
  • __tmp_rar_sfx_access_check_149796
  • uRgBTn.SII
  • UXpCwuTvSZ.exe
  • lJwwOuSYyRXG.GRB
  • rYpFHPKAy.PBM
  • %User Profile%\HAnXQouasfo\HAnXQouasfo.nfo
  • %User Temp%\x.html
  • %User Profile%\HAnXQouasfo\HAnXQouasfo.svr
  • %Windows%\WinDir\Server.exe

Step 7

Search and delete these folders

[ 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.
  • %System Root%\Documents and Settings\Wilbert
  • %User Profile%\kc1939z1z477
  • %User Profile%\Windows\HAnXQouasfo
  • %Windows%\WinDir

Step 8

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