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TROJ_FAM_00000a000.TOMA

October 12, 2012
 ALIASES:

Trojan:Win32/VB (Microsoft); Generic VB.au (McAfee); Trojan Horse (Symantec); Trojan.Win32.VB.fqx (Kaspersky); Trojan.Agent.VB.AZC (FSecure)

 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 modifies files, disabling programs and applications from properly running.

  TECHNICAL DETAILS

File Size:

58,378 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

25 Apr 2012

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%\InstallDir\Server.exe

(Note: %System% is the Windows system folder, which is usually C:\Windows\System on Windows 98 and ME, C:\WINNT\System32 on Windows NT and 2000, or C:\Windows\System32 on Windows XP and Server 2003.)

It creates the following folders:

  • %System%\InstallDir

(Note: %System% is the Windows system folder, which is usually C:\Windows\System on Windows 98 and ME, C:\WINNT\System32 on Windows NT and 2000, or C:\Windows\System32 on Windows XP and Server 2003.)

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\Run
HKLM = "%System%\InstallDir\Server.exe"

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

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Active Setup\Installed Components\{10P08NLY-ESX2-4DXV-Q1P6-FT82Y65BJ67W}
StubPath = "%System%\InstallDir\Server.exe"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Active Setup\Installed Components\{10P08NLY-ESX2-4DXV-Q1P6-FT82Y65BJ67W}
StubPath = "%System%\InstallDir\Server.exe restart"

Other System Modifications

This Trojan modifies the following files:

  • %User Profile%\Application Data\Microsoft

(Note: %User Profile% is the current user's profile folder, which is usually C:\Windows\Profiles\{user name} on Windows 98 and ME, C:\WINNT\Profiles\{user name} on Windows NT, and C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003.)

It deletes the following files:

  • %User Profile%\Windows\NFin2548Ez6fD52le.xtr

(Note: %User Profile% is the current user's profile folder, which is usually C:\Windows\Profiles\{user name} on Windows 98 and ME, C:\WINNT\Profiles\{user name} on Windows NT, and C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003.)

It adds the following registry keys:

HKEY_CURRENT_USER\SOFTWARE\XtremeRAT

HKEY_CURRENT_USER\SOFTWARE\NFin2548Ez6fD52le

HKEY_LOCAL_MACHINE\Software\Microsoft\
Active Setup\Installed Components\{10P08NLY-ESX2-4DXV-Q1P6-FT82Y65BJ67W}

It adds the following registry entries:

HKEY_CURRENT_USER\Software\XtremeRAT
Mutex = "NFin2548Ez6fD52le"

HKEY_CURRENT_USER\Software\NFin2548Ez6fD52le
ServerStarted = "24/04/2012 17:29:27"

HKEY_CURRENT_USER\Software\NFin2548Ez6fD52le
ServerName = "%System%\InstallDir\Server.exe"

It modifies the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
DirectDraw\MostRecentApplication
Name = "svchost.exe"

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

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
DirectDraw\MostRecentApplication
ID = "4117ed6"

(Note: The default value data of the said registry entry is 41107b81.)

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
DirectDraw\MostRecentApplication
Name = "iexplore.exe"

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

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
DirectDraw\MostRecentApplication
ID = "4117b81"

(Note: The default value data of the said registry entry is 41107b81.)

Dropping Routine

This Trojan drops the following files:

  • %User Profile%\Microsoft\Crypto
  • %User Profile%\Crypto\RSA
  • %User Profile%\RSA\S-1-5-21-4025279379-4087772427-2915903831-500
  • %User Temp%\x.html

(Note: %User Profile% is the current user's profile folder, which is usually C:\Windows\Profiles\{user name} on Windows 98 and ME, C:\WINNT\Profiles\{user name} on Windows NT, and C:\Documents and Settings\{user name} on Windows 2000, XP, and Server 2003.. %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.)

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine:

9.200

Step 1

For Windows XP and Windows Server 2003 users, before doing any scans, please make sure you disable System Restore to allow full scanning of your computer.

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_CURRENT_USER\SOFTWARE
    • XtremeRAT
  • In HKEY_CURRENT_USER\SOFTWARE
    • NFin2548Ez6fD52le
  • In HKEY_LOCAL_MACHINE\Software\Microsoft\Active Setup\Installed Components
    • {10P08NLY-ESX2-4DXV-Q1P6-FT82Y65BJ67W}

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\Run
    • HKLM = "%System%\InstallDir\Server.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • HKCU = "%System%\InstallDir\Server.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Active Setup\Installed Components\{10P08NLY-ESX2-4DXV-Q1P6-FT82Y65BJ67W}
    • StubPath = "%System%\InstallDir\Server.exe"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Active Setup\Installed Components\{10P08NLY-ESX2-4DXV-Q1P6-FT82Y65BJ67W}
    • StubPath = "%System%\InstallDir\Server.exe restart"
  • In HKEY_CURRENT_USER\Software\XtremeRAT
    • Mutex = "NFin2548Ez6fD52le"
  • In HKEY_CURRENT_USER\Software\NFin2548Ez6fD52le
    • ServerStarted = "24/04/2012 17:29:27"
  • In HKEY_CURRENT_USER\Software\NFin2548Ez6fD52le
    • ServerName = "%System%\InstallDir\Server.exe"

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_LOCAL_MACHINE\SOFTWARE\Microsoft\DirectDraw\MostRecentApplication
    • From: Name = "svchost.exe"
      To: Name = ""iexplore.exe""
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\DirectDraw\MostRecentApplication
    • From: ID = "4117ed6"
      To: ID = ""41107b81""
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\DirectDraw\MostRecentApplication
    • From: Name = "iexplore.exe"
      To: Name = ""iexplore.exe""
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\DirectDraw\MostRecentApplication
    • From: ID = "4117b81"
      To: ID = ""41107b81""

Step 6

Search and delete these files

[ Learn More ]
There may be some component 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%\Microsoft\Crypto
  • %User Profile%\Crypto\RSA
  • %User Profile%\RSA\S-1-5-21-4025279379-4087772427-2915903831-500
  • %User Temp%\x.html

Step 7

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%\InstallDir

Step 8

Restart in normal mode and scan your computer with your Trend Micro product for files detected as TROJ_FAM_00000a000.TOMA. 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 9

Restore deleted/modified files and/or registry entries from backup

*Note: Only Microsoft-related files/keys/values will be restored. If this malware/grayware also deleted registry keys/values related to programs that are not from Microsoft, please reinstall those programs on your computer.

    • %User Profile%\Application Data\Microsoft

Step 10

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.

  • %User Profile%\Windows\NFin2548Ez6fD52le.xtr


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