ALIASES:

Backdoor:Win32/Haxdoor.CN (Microsoft); BackDoor-BAC.gen.b (McAfee); Backdoor.Haxdoor.D (Symantec); Backdoor.Win32.Haxdoor.cg (Kaspersky); BehavesLike.Win32.Malware.ssc (mx-v) (Sunbelt); Backdoor.Generic.177779 (FSecure)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted:

  • In the wild: Yes

  OVERVIEW

This backdoor 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: 51,987 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 04 Oct 2012

Arrival Details

This backdoor 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 backdoor drops the following copies of itself into the affected system:

  • mszx23.exe

It creates the following folders:

  • %User Temp%\01808300

(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.)

Autostart Technique

This backdoor registers as a system service to ensure its automatic execution at every system startup by adding the following registry keys:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\
Services\VFILT

Other System Modifications

This backdoor deletes the following files:

  • %User Startup%\winupdt.exe
  • %Windows%\dt163.dt

(Note: %User Startup% is the current user's Startup folder, which is usually C:\Windows\Profiles\{user name}\Start Menu\Programs\Startup on Windows 98 and ME, C:\WINNT\Profiles\{user name}\Start Menu\Programs\Startup on Windows NT, and C:\Documents and Settings\{User name}\Start Menu\Programs\Startup.. %Windows% is the Windows folder, which is usually C:\Windows or C:\WINNT.)

It adds the following registry keys:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon\
Notify\drct16

HKEY_CURRENT_USER\SOFTWARE\Microsoft\
Internet Account Manager\Accounts

HKEY_CURRENT_USER\Identities\{8A24C031-62FE-4BF5-94F0-BFD4FBCD674B}\
SOFTWARE\Microsoft\Internet Account Manager\
Accounts

It adds the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Control
Impersonate = "[19537978053907595610]"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Control
StackSize = "3:10"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon\
Notify\drct16
DllName = "drct16.dll"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon\
Notify\drct16
Startup = "MeMessager"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon\
Notify\drct16
Impersonate = "1"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon\
Notify\drct16
Asynchronous = "1"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon\
Notify\drct16
MaxWait = "1"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Control\Session Manager\Memory Management
EnforceWriteProtection = "0"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion
hws = "558"

It modifies the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
DirectDraw\MostRecentApplication
Name = "mszx23.exe"

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

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
DirectDraw\MostRecentApplication
ID = "f64f"

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

Dropping Routine

This backdoor drops the following files:

  • i.a3d
  • fltr.a3d
  • tnfl.a3d
  • redir.a3d
  • drct16.dll
  • cz.dll
  • vdmt16.sys
  • hz.sys
  • winlow.sys
  • wz.sys
  • p2.ini
  • %Windows%\dt163.dt

(Note: %Windows% is the Windows folder, which is usually C:\Windows or C:\WINNT.)

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_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services
    • VFILT
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\Notify
    • drct16
  • In HKEY_CURRENT_USER\SOFTWARE\Microsoft\Internet Account Manager
    • Accounts
  • In HKEY_CURRENT_USER\Identities\{8A24C031-62FE-4BF5-94F0-BFD4FBCD674B}\SOFTWARE\Microsoft\Internet Account Manager
    • Accounts

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\SYSTEM\ControlSet001\Control
    • Impersonate = "[19537978053907595610]"
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control
    • StackSize = "3:10"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\Notify\drct16
    • DllName = "drct16.dll"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\Notify\drct16
    • Startup = "MeMessager"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\Notify\drct16
    • Impersonate = "1"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\Notify\drct16
    • Asynchronous = "1"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon\Notify\drct16
    • MaxWait = "1"
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\Session Manager\Memory Management
    • EnforceWriteProtection = "0"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion
    • hws = "558"

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 = "mszx23.exe"
      To: Name = ""iexplore.exe""
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\DirectDraw\MostRecentApplication
    • From: ID = "f64f"
      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.
  • i.a3d
  • fltr.a3d
  • tnfl.a3d
  • redir.a3d
  • drct16.dll
  • cz.dll
  • vdmt16.sys
  • hz.sys
  • winlow.sys
  • wz.sys
  • p2.ini
  • %Windows%\dt163.dt

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.
  • %User Temp%\01808300

Step 8

Restart in normal mode and scan your computer with your Trend Micro product for files detected as BKDR_HAXDOOR.CC. 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 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 Startup%\winupdt.exe
  • %Windows%\dt163.dt


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