Analysis by: Janus Agcaoili
ALIASES:

Trojan:Win32/Folyris.A (Microsoft)

 PLATFORM:

Windows

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: No

  • 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.

It modifies certain registry entries to disable the Automatic Windows Update feature. This action prevents the affected system to be notified when critical Windows updates are available.

It executes commands from a remote malicious user, effectively compromising the affected system. However, as of this writing, the said sites are inaccessible.

It modifies the Internet Explorer Zone Settings.

It deletes the initially executed copy of itself.

  TECHNICAL DETAILS

File Size: 510,711 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 31 Mar 2014
Payload: Compromises system security, Steals information

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 a copy of itself in the following folders using different file names:

  • %Application Data%\Microsoft\update.exe
  • %Windows%\-1474012438\taskhost

(Note: %Application Data% is the Application Data folder, where it usually is C:\Documents and Settings\{user name}\Application Data on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Roaming on Windows Vista (32- and 64-bit), Windows 7 (32- and 64-bit), Windows 8 (32- and 64-bit), Windows 8.1 (32- and 64-bit), Windows Server 2008, and Windows Server 2012.. %Windows% is the Windows folder, where it usually is C:\Windows on all Windows operating system versions.)

It drops the following copies of itself into the affected system and executes them:

  • %User Profile%\dwm

(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 adds the following mutexes to ensure that only one of its copies runs at any one time:

  • BACKUP_-1474012438
  • MAIN_-1474012438
  • UPDATE_-1474012438
  • UNINSTALL_-1474012438

It terminates the execution of the copy it initially executed and executes the copy it drops instead.

It terminates itself if it finds the following processes in the affected system's memory:

  • SbieDll.dll
  • snxhk.dll
  • dbghelp.dll

Autostart Technique

This backdoor creates the following registry entries to enable automatic execution of dropped component at every system startup:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
Facebook Update = "%Application Data%\Microsoft\update.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
Explorer\Run
Facebook Update = "%Application Data%\Microsoft\update.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows NT\CurrentVersion\Winlogon
shell = "%Application Data%\Microsoft\update.exe,explorer.exe"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\RunOnce
*-1474012438 = "%Windows%\-1474012438\taskhost"

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\RunOnce
*-1474012438 = "%Windows%\-1474012438\taskhost"

It drops the following shortcut pointing to its copy in the User Startup folder to enable its automatic execution at every system startup:

  • %User Startup%\Facebook.lnk

(Note: %User Startup% is the current user's Startup folder, which is usually C:\Documents and Settings\{user}\Start Menu\Programs\Startup on Windows 2000 and XP, and C:\Documents and Settings\{User name}\Start Menu\Programs\Startup on Windows Vista, 7, and 8.)

Other System Modifications

This backdoor deletes the following files:

  • {Malware path}\{Malware Name}:Zone.Identifier

It modifies the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
Explorer
NoFolderOptions = 1

(Note: The default value data of the said registry entry is 0.)

It modifies the following registry entries to disable the Active Windows Update feature:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
Explorer
NoWindowsUpdate = 1

(Note: The default value data of the said registry entry is 0.)

It modifies the following registry entries to hide files with Hidden attributes:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced
Hidden = 2

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Explorer\
Advanced\Folder\SuperHidden
CheckedValue = 1

(Note: The default value data of the said registry entry is 0.)

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Policies\
Explorer
ShowSuperHidden = 0

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

Backdoor Routine

This backdoor executes the following commands from a remote malicious user:

  • Download/Update itself
  • Open Skype Application (If Available)
  • Open browser applications and visit arbitrary sites
  • Search and Download files from affected systems
  • Lock users out of affected system
  • Terminate malware from the affected system
  • Uninstall malware from the affected system
  • Perform DDOS attacks:
    - HTTP GET/POST Flood
    - BANDWIDTH Flood
    - RUDY Flood
    - SLOWLORIS Flood
    - ARME Flood
    - UDP Flood
    - ECF Flood
    - BROWSER BASED Flood
  • Terminate Process/es from affected systems
  • Delete file/s from affected systems

It connects to the following URL(s) to send and receive commands from a remote malicious user:

  • http://{BLOCKED}thit.x10.mx/panel/gate.php

It posts the following information to its command and control (C&C) server:

  • a = URL (Base64 Encoded)
  • b = "|type:on_exec|uid:%s|priv:%s|arch:x%s|gend:%s|cores:%i|os:%s|ver:%s|net:%s|new:" (Encrypted)
  • c = Data marker of the response (Base64 Encoded)

However, as of this writing, the said sites are inaccessible.

Process Termination

This backdoor terminates the following processes if found running in the affected system's memory:

  • autoruns.exe

Web Browser Home Page and Search Page Modification

This backdoor modifies the Internet Explorer Zone Settings.

Information Theft

This backdoor gathers the following data:

  • UID
  • PRIVILEDGE (Admin/User/Etc)
  • ARCHITECTURE (x86/x64)
  • GENDER (Laptop/Desktop/etc)
  • NUMBER OF CORES
  • OS
  • OS VERSION
  • .NET VERSION

Other Details

This backdoor sets the attributes of the following file(s) to Hidden and System:

  • %Windows%\-1474012438\taskhost

(Note: %Windows% is the Windows folder, where it usually is C:\Windows on all Windows operating system versions.)

It checks for the presence of the following process(es):

  • explorer.exe <- Child process of either "dwm" or "taskhost"
  • (Note: This routine is used to check and ensure that the malware is running)

It does the following:

  • Disables Windows Task Manager
  • Flush DNS Cache

It performs DNS requests to the following sites:

  • http://{BLOCKED}thit.x10.mx

It deletes the initially executed copy of itself

  SOLUTION

Minimum Scan Engine: 9.750
FIRST VSAPI PATTERN FILE: 10.698.05
FIRST VSAPI PATTERN DATE: 31 Mar 2014
VSAPI OPR PATTERN File: 10.699.00
VSAPI OPR PATTERN Date: 01 Apr 2014

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

Note that not all files, folders, and registry keys and entries are installed on your computer during this malware's/spyware's/grayware's execution. This may be due to incomplete installation or other operating system conditions. If you do not find the same files/folders/registry information, please proceed to the next step.

Step 3

Restart in Safe Mode

[ Learn More ]

Step 4

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 Startup%\Facebook.lnk

Step 5

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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\RunOnce
    • *-1474012438 = C:\WINDOWS\-1474012438\taskhost

  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\RunOnce
    • *-1474012438 = C:\WINDOWS\-1474012438\taskhost

  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • Facebook Update = %Application Data%\Microsoft\update.exe

  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer\Run
    • Facebook Update = %Application Data%\Microsoft\update.exe

  • In HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\Winlogon
    • shell = %Application Data%\Microsoft\update.exe,explorer.exe

Step 6

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\Windows\CurrentVersion\Policies\Explorer
    • From: NoWindowsUpdate = 1
      To: NoWindowsUpdate = 0
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
    • From: Hidden = 2
      To: Hidden = 1
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced\Folder\SuperHidden
    • From: CheckedValue = 1
      To: CheckedValue = 0
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer
    • From: NoFolderOptions = 1
      To: NoFolderOptions = 0
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer
    • From: ShowSuperHidden = 0
      To: ShowSuperHidden = 1

Step 7

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


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