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:
- %User Profile%\SubFolder\winlogon.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.)
It creates the following folders:
- %User Profile%\Application Data\SubFolder
- %User Profile%\SubFolder\SubFolder
- %User Profile%\My Documents\MSDCSC
(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.)
Autostart Technique
This backdoor adds the following registry entries to enable its automatic execution at every system startup:
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
Winlogon = "%User Profile%\SubFolder\winlogon.exe"
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
Winlogon = "%User Profile%\SubFolder\winlogon.exe"
HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
Microsoft Update = "%User Profile%\MSDCSC\msdcsc.exe"
It modifies the following registry entries to ensure it automatic execution at every system startup:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\Winlogon
UserInit = "%System%\userinit.exe,%User Profile%\MSDCSC\msdcsc.exe"
(Note: The default value data of the said registry entry is %Windows%\system32\userinit.exe,.)
Other System Modifications
This backdoor modifies the following file(s):
- %Application Data%\GDIPFONTCACHEV1.DAT
(Note: %Application Data% is the current user's Application Data folder, which is usually C:\Documents and Settings\{user name}\Application Data on Windows 2000, XP, and Server 2003, or C:\Users\{user name}\AppData\Roaming on Windows Vista and 7.)
It adds the following registry keys:
HKEY_CURRENT_USER\Software\DC3_FEXEC
It modifies the following registry entries:
HKEY_CURRENT_USER\Software\Microsoft\
GDIPlus
FontCachePath = "%Application Data%"
(Note: The default value data of the said registry entry is %User Profile%\Local Settings\Application Data.)
Dropping Routine
This backdoor drops the following files:
- %User Profile%\SubFolder\csrss.exe
- %User Profile%\MSDCSC\msdcsc.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.)
This report is generated via an automated analysis system.
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
Identify and delete files detected as BKDR_FYNLOS.TMC using either the Startup Disk or Recovery Console
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To identify and delete the malware/grayware file:
• On Windows XP and Server 2003 systems:
- Scan your computer with your Trend Micro product and then take note of the names of the malware/grayware files detected.
- Click Start>Run. In the Open input box, type secpol.msc and press Enter.
- In the left panel, double-click Local Policies>Security Options.
- In the right panel, double-click Recovery Console: Allow floppy copy and access to all drives and folders.
- Select Enabled and click OK.
- Insert the Windows Installation CD into the CD drive, then restart your computer.
- When prompted, press any key to boot from the CD.
- On the main menu, type r to go to the Recovery Console.
- Type the number that corresponds to the drive and directory that contains Windows (usually C:\WINDOWS) and press Enter.
- Type the Administrator password and press Enter.
- In the input box, type the following then press Enter:
SET AllowAllPaths = TRUE
del "{malware/grayware path and file name}" - Type exit and press Enter to restart the system normally.
• On Windows Vista, 7, and Server 2008 (R2) systems:
- Scan your computer with your Trend Micro product and then take note of the names of the malware/grayware files detected.
- Insert your Windows Installation DVD in the DVD drive, then Press the restart button.
- When prompted, press any key to boot from the CD.
- Depending on your Windows Installation DVD, you might be required to select the installation language. Then on the Install Windows window, choose your language, locale, and keyboard layout or input method. Click Next, then click Repair your computer.
- Select Use recovery tools that can help fix problems starting Windows. Select your installation of Windows. Click Next.
- If the Startup Repair window appears, click Cancel, Yes, then Finish.
- In the System Recovery Options window, click Command Prompt.
- In the Command Prompt window, type the following then press Enter:
BootRec.exe /fixmbr
del "{malware/grayware path and file name}" - Type exit and press Enter to close the Command Prompt window.
- Click Restart to restart the system normally.
• On Windows 8, 8.1, and Server 2012 (R2) systems:
- Scan your computer with your Trend Micro product and then take note of the names of the malware/grayware files detected.
- Insert your Windows Installation DVD in the DVD drive, then restart your computer.
- When prompted, press any key to boot from the DVD.
- Depending on your Windows Installation DVD, you might be required to select the keyboard layout. Then on the Windows Setup window, choose your language, locale, and input method. Click Next, then click Repair your computer.
- Click Troubleshoot>Advanced Options>Command Prompt.
- In the Command Prompt window, type the following then press Enter:
BootRec.exe /fixmbr
del "{malware/grayware path and file name}" - Type exit and press Enter to close the Command Prompt window.
- Click Continue to restart the system normally.
Step 3
Delete this registry key
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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
To delete the registry key this malware/grayware created:
- Open Registry Editor.
» For Windows 2000, Windows XP, and Windows Server 2003 users, click Start>Run, type regedit in the text box provided, and then press Enter.
» For Windows Vista, Windows 7, and Windows Server 2008 (R2) users, click the Start button, type regedit in the Search input field then press Enter.
» For Windows 8, Windows 8.1, and Windows Server 2012 (R2) users, right-click on the lower left corner of the screen, click Run, type regedit in the text box provided, and then press Enter. - In the left panel, double-click the following:
HKEY_CURRENT_USER>Software - Still in the left panel, locate and delete the key:
DC3_FEXEC - Close Registry Editor.
Step 4
Delete this registry value
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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\Run
- Winlogon = "%User Profile%\SubFolder\winlogon.exe"
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
- Winlogon = "%User Profile%\SubFolder\winlogon.exe"
- In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
- Microsoft Update = "%User Profile%\MSDCSC\msdcsc.exe"
To delete the registry value this malware/grayware created:
- Open Registry Editor.
» For Windows 2000, Windows XP, and Windows Server 2003 users, click Start>Run, type regedit in the text box provided, and then press Enter.
» For Windows Vista, Windows 7, and Windows Server 2008 (R2) users, click the Start button, type regedit in the Search input field then press Enter.
» For Windows 8, Windows 8.1, and Windows Server 2012 (R2) users, right-click on the lower-left corner of the screen, click Run, type regedit in the text box provided, and then press Enter. - In the left panel, double-click the following:
HKEY_CURRENT_USER>Software>Microsoft>Windows>CurrentVersion>Run - In the right panel, locate and delete the entry:
Winlogon = "%User Profile%\SubFolder\winlogon.exe" - In the left panel, double-click the following:
HKEY_LOCAL_MACHINE>SOFTWARE>Microsoft>Windows>CurrentVersion>Run - In the right panel, locate and delete the entry:
Winlogon = "%User Profile%\SubFolder\winlogon.exe" - Again In the right panel, locate and delete the entry:
Microsoft Update = "%User Profile%\MSDCSC\msdcsc.exe" - Close Registry Editor.
Step 5
Restore these modified registry values
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Important:Editing the Windows Registry incorrectly can lead to irreversible system malfunction. Please do this only if you know how to or you can seek your system administrator's help. You may also check out this Microsoft article first before modifying your computer's registry.
- In HKEY_CURRENT_USER\Software\Microsoft\GDIPlus
- From: FontCachePath = "%Application Data%"
To: FontCachePath = ""%User Profile%\Local Settings\Application Data""
- In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
- From: UserInit = "%System%\userinit.exe,%User Profile%\MSDCSC\msdcsc.exe"
To: UserInit = ""%Windows%\system32\userinit.exe,""
To restore registry values this malware/grayware modified:
- Open Registry Editor. To do this:
- On Windows 2000, XP, and Server 2003:
Click Start>Run, type REGEDIT in the text box provided, and then press Enter. - On Windows Vista, 7, and Server 2008 (R2):
Click the Start button, type REGEDIT in the Search input field then press Enter. - On Windows 8, 8.1, and Server 2012 (R2):
Right-click on the lower left corner of the screen and click Run, type REGEDIT in the Run input field, and then press Enter.
- In the left panel, double-click the following:
HKEY_CURRENT_USER>Software>Microsoft>GDIPlus - In the right panel, locate the registry value:
FontCachePath = "%Application Data%" - Right-click on the value name and choose Modify. Change the value data of this entry to:
FontCachePath = "%User Profile%\Local Settings\Application Data" - In the left panel, double-click the following:
HKEY_LOCAL_MACHINE>SOFTWARE>Microsoft>Windows NT>CurrentVersion>Winlogon - In the right panel, locate the registry value:
UserInit = "%System%\userinit.exe,%User Profile%\MSDCSC\msdcsc.exe" - Right-click on the value name and choose Modify. Change the value data of this entry to:
UserInit = "%Windows%\system32\userinit.exe," - Close Registry Editor.
Step 6
Search and delete these components
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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.
- %User Profile%\SubFolder\csrss.exe
- %User Profile%\MSDCSC\msdcsc.exe
To manually delete a malware/grayware file from an affected system:
• For Windows 2000, Windows XP, and Windows Server 2003:
- Right-click Start then click Search....
- In the File name* input box, type the following:
- %User Profile%\SubFolder\csrss.exe
- %User Profile%\MSDCSC\msdcsc.exe
- In the Look In drop-down list, select My Computer then press Enter.
- Once located, select the file then press SHIFT+DELETE to delete it.
*Note: The file name input box title varies depending on the Windows version (e.g. Search for files or folders named or All or part of the file name.).
• For Windows Vista, Windows 7, Windows Server 2003 (R2), Windows 8, Windows 8.1, and Windows Server 2012 (R2):
- Open a Windows Explorer window.
- For Windows Vista, 7, and Server 2008 (R2) users, click Start>Computer.
- For Windows 8, 8.1, and Server 2012 (R2) users, right-click on the lower left corner of the screen,then click File Explorer.
- In the Search Computer/This PC input box, type:
- %User Profile%\SubFolder\csrss.exe
- %User Profile%\MSDCSC\msdcsc.exe
- Once located, select the file then press SHIFT+DELETE to delete it.
*Note: Read the following Microsoft page if these steps do not work on Windows 7.
Step 7
Search and delete these folders
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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 Profile%\Application Data\SubFolder
- %User Profile%\SubFolder\SubFolder
- %User Profile%\My Documents\MSDCSC
To delete malware/grayware/spyware folders:
For Windows 2000, Windows XP, and Windows Server 2003:
- Right-click Start then click Search... or Find..., depending on the version of Windows you are running.
- In the File name* input box, type:
- %User Profile%\Application Data\SubFolder
- %User Profile%\SubFolder\SubFolder
- %User Profile%\My Documents\MSDCSC
- In the Look In drop-down list, select My Computer, then press Enter.
- Once located, select the folder then press SHIFT+DELETE to permanently delete the folder.
- Repeat steps 2 to 4 for the remaining folders:
- %User Profile%\Application Data\SubFolder
- %User Profile%\SubFolder\SubFolder
- %User Profile%\My Documents\MSDCSC
*Note: The file name input box title varies depending on the Windows version (e.g. Search for files or folders named or All or part of the file name.).
For Windows Vista, Windows 7, Windows Server 2003 (R2), Windows 8, Windows 8.1, and Windows Server 2012 (R2):
- Open a Windows Explorer window.
- For Windows Vista, 7, and Server 2008 (R2) users, click Start>Computer.
- For Windows 8, 8.1, and Server 2012 (R2) users, right-click on the lower left corner of the screen, then click File Explorer.
- In the Search Computer/This PC input box, type:
- %User Profile%\Application Data\SubFolder
- %User Profile%\SubFolder\SubFolder
- %User Profile%\My Documents\MSDCSC
- Once located, select the file then press SHIFT+DELETE to permanently delete the folder.
- Repeat steps 2-3 for the remaining folders:
- %User Profile%\Application Data\SubFolder
- %User Profile%\SubFolder\SubFolder
- %User Profile%\My Documents\MSDCSC
*Note: Read the following Microsoft page if these steps do not work on Windows 7.
Step 8
Scan your computer with your Trend Micro product to delete files detected as BKDR_FYNLOS.TMC. 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.
- %Application Data%\GDIPFONTCACHEV1.DAT
