Analysis by: Kathleen Notario
 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

This Trojan moves specific files in the certain directories. It also modifies the attributes of files found in the affected system into Hidden, to trick the users that the files have been deleted.

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 deletes the initially executed copy of itself.

  TECHNICAL DETAILS

File Size: 404,368 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 25 Oct 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 files:

  • %System Root%\Documents and Settings\All Users\Application Data\{random filename2}
  • %System Root%\Documents and Settings\All Users\Application Data\{random filename2}.exe

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

It drops the following copies of itself into the affected system:

  • %System Root%\Documents and Settings\All Users\Application Data\{random filename1}.exe

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

It creates the following folders:

  • %User Temp%\smtmp
  • %User Temp%\smtmp\1
  • %User Temp%\smtmp\2
  • %User Temp%\smtmp\3
  • %User Temp%\smtmp\4

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

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
{random file name1} = "%System Root%\Documents and Settings\All Users\Application Data\{random filename1}.exe"

Other System Modifications

This Trojan adds the following registry entries:

HKEY_CURRENT_USER\Control Panel
7f6b3266-31c5-43a8-9547-e7911ad6fb33 = ""

HKEY_CURRENT_USER\Control Panel
nsreg = "{hex value}"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
ActiveDesktop
NoChangingWallPaper = "1"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
Associations
LowRiskFileTypes = ".zip;.rar;.nfo;.txt;.exe;.bat;.com;.cmd;.reg;.msi;.htm;.html;.gif;.bmp;.jpg;.avi;.mpg;.mpeg;.mov;.mp3;.m3u;.wav;.scr;"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
Attachments
SaveZoneInformation = "1"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
System
DisableTaskMgr = "1"

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

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\policies\
system
DisableTaskMgr = "1"

It modifies the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\Download
CheckExeSignatures = "no"

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

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

(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.)

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

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

Other Details

This Trojan deletes the initially executed copy of itself

NOTES:

It moves specific files in the following directories:

Operating System major version is 5 (XP, 2000, 2003):

From: %System Root%\Documents and Settings\All Users\Start Menu\
To: %User Temp%\smtmp\1\

From: %User Profile%\Application Data\Microsoft\Internet Explorer\Quick Launch\
To: %User Temp%\smtmp\2\

From: %System Root%\Documents and Settings\All Users\Desktop\
To: %User Temp%\smtmp\4\

Operating System major version is 6 (Vista, 2008, 7)

From: %System Root%\ProgramData\Start Menu\
To: %User Temp%\smtmp\1\

From: %User Profile%\Application Data\Roaming\Microsoft\Internet Explorer\Quick Launch\
To: %User Temp%\smtmp\2\

From: %User Profile%\Application Data\Roaming\Microsoft\Internet Explorer\Quick Launch\User Pinned\TaskBar\
To: %User Temp%\smtmp\3\

From: %System Root%\ProgramData\Desktop\
To: %User Temp%\smtmp\4\

It also modifies the attributes of files found in the affected system into Hidden, to trick the users that the files have been deleted.

  SOLUTION

Minimum Scan Engine: 9.200
FIRST VSAPI PATTERN FILE: 8.520.08
FIRST VSAPI PATTERN DATE: 25 Oct 2011

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 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
    • {random filename1} = "%System Root%\Documents and Settings\All Users\Application Data\{random filename1}.exe"
  • In HKEY_CURRENT_USER\Control Panel
    • 7f6b3266-31c5-43a8-9547-e7911ad6fb33 = ""
  • In HKEY_CURRENT_USER\Control Panel
    • nsreg = "{hex value}"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\ActiveDesktop
    • NoChangingWallPaper = "1"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Associations
    • LowRiskFileTypes = ".zip;.rar;.nfo;.txt;.exe;.bat;.com;.cmd;.reg;.msi;.htm;.html;.gif;.bmp;.jpg;.avi;.mpg;.mpeg;.mov;.mp3;.m3u;.wav;.scr;"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Attachments
    • SaveZoneInformation = "1"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\System
    • DisableTaskMgr = "1"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer
    • NoDesktop = "1"
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\system
    • DisableTaskMgr = "1"

Step 4

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\Internet Explorer\Download
    • From: CheckExeSignatures = "no"
      To: "yes"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
    • From: Hidden = "0"
      To: "1"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
    • From: ShowSuperHidden = "0"
      To: "1"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
    • From: TaskbarGlomming = "0"
      To: "1"

Step 5

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.  
  • %System Root%\Documents and Settings\All Users\Application Data\{random file name2}
  • %System Root%\Documents and Settings\All Users\Application Data\{random file name2}.exe

Step 6

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

NOTES:

To unhide the files hidden by this malware, perform the following steps:

  1. Open a Command Prompt.

    For Windows 2000, Windows XP, and Windows Server 2003 users:
    Click Start > Run, type CMD in the text box provided, and then press Enter.

    For Windows Vista and Windows 7 users:
    Click the Start button, type CMD in the Search input field then press Enter.

  2. For every drive in the computer, type the following command:
    • •attrib -h {drive letter}:\*.* /s /d
  3. Close Command Prompt. Type exit then press Enter.

    To Restore Files to its Original Location:

    Open %User Temp%\smtmp and copy the files as follows:

    If operating system major version is 5 (XP, 2000, 2003):

    From: %User Temp%\smtmp\1\
    To: %System Root%\Documents and Settings\All Users\Start Menu\

    From: %User Temp%\smtmp\2\
    To: %User Profile%\Application Data\Microsoft\Internet Explorer\Quick Launch\

    From: %User Temp%\smtmp\4\
    To: %System Root%\Documents and Settings\All Users\Desktop\

    If operating system major version is 6 (Vista, 2008, 7)

    From: %User Temp%\smtmp\1\
    To: %System Root%\ProgramData\Start Menu\

    From: %User Temp%\smtmp\2\
    To: %User Profile%\Application Data\Roaming\Microsoft\Internet Explorer\Quick Launch\

    From: %User Temp%\smtmp\3\
    To: %User Profile%\Application Data\Roaming\Microsoft\Internet Explorer\Quick Launch\User Pinned\TaskBar\

    From: %User Temp%\smtmp\4\
    To: %System Root%\ProgramData\Desktop\

  4. After moving the files, delete the folder %User Temp%\smtmp.


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