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TROJ_REFROS.SMUJ

June 24, 2013
 ALIASES:

Backdoor:Win32/Bifrose.AE (Microsoft); Trojan.Gen (Symantec); Trojan-Spy.Win32.Zbot.bhfu (Kaspersky); Trojan.Win32.Generic!BT (Sunbelt)

 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.

  TECHNICAL DETAILS

File Size:

149,867 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

09 Nov 2011

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 drops the following copies of itself into the affected system:

  • %System%\Win32\Win32.exe

(Note: %System% is the Windows system folder, which is usually C:\Windows\System32.)

It creates the following folders:

  • %System%\Win32

(Note: %System% is the Windows system folder, which is usually C:\Windows\System32.)

Autostart Technique

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

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Active Setup\Installed Components\{35F5436C-D1C7-2E0B-ACBD-D83D2600C47A}
stubpath = "%System%\Win32\Win32.exe s"

Other System Modifications

This Trojan deletes the following files:

  • %System%\Win32\Win32.exe

(Note: %System% is the Windows system folder, which is usually C:\Windows\System32.)

It adds the following registry keys:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Active Setup\Installed Components\{35F5436C-D1C7-2E0B-ACBD-D83D2600C47A}

HKEY_LOCAL_MACHINE\SOFTWARE\Yahoo

HKEY_CURRENT_USER\SOFTWARE\Yahoo

It adds the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Yahoo
nck = {random values}

HKEY_CURRENT_USER\Software\Yahoo
klg = {random values}

HKEY_CURRENT_USER\Software\Yahoo
plg1 = {random values}

Dropping Routine

This Trojan drops the following files:

  • %User Profile%\Application Data\addons.dat

(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.)

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine:

9.200

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

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_LOCAL_MACHINE\SOFTWARE\Microsoft\Active Setup\Installed Components
    • {35F5436C-D1C7-2E0B-ACBD-D83D2600C47A}
  • In HKEY_LOCAL_MACHINE\SOFTWARE
    • Yahoo
  • In HKEY_CURRENT_USER\SOFTWARE
    • Yahoo

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\Active Setup\Installed Components\{35F5436C-D1C7-2E0B-ACBD-D83D2600C47A}
    • stubpath="%System%\Win32\Win32.exe s"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Yahoo
    • nck={random values}
  • In HKEY_CURRENT_USER\Software\Yahoo
    • klg={random values}
  • In HKEY_CURRENT_USER\Software\Yahoo
    • plg1={random values}

Step 5

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. %System%\Win32

Step 6

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. %User Profile%\Application Data\addons.dat

Step 7

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

Step 8

Restore this file from backup only Microsoft-related files will be restored. If this malware/grayware also deleted files related to programs that are not from Microsoft, please reinstall those programs on you computer again. %System%\Win32\Win32.exe


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