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BKDR_FYNLOSKI.XXQS

October 08, 2015
 Analysis by: Mar Philip Elaurza
 ALIASES:

Backdoor:Win32/Fynloski (MICROSOFT), TR/AD.Fynloski.Y.414 (Avira), W32/Msil.AYM (exact) (FPROT)

 PLATFORM:

Windows

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Via email, Downloaded from the Internet


This backdoor arrives as attachment to mass-mailed email messages. It arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It executes commands from a remote malicious user, effectively compromising the affected system. It connects to a website to send and receive information. However, as of this writing, the said sites are inaccessible.

  TECHNICAL DETAILS

File Size:

279,040 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

19 Aug 2015

Payload:

Connects to URLs/IPs, Compromises system security, Logs keystrokes

Arrival Details

This backdoor arrives as attachment to mass-mailed email messages.

It 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 and executes them:

  • %Application Data%\i9FwLiiVlr\oznz68mk.exe

(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.)

It creates the following folders:

  • %Application Data%\i9FwLiiVlr
  • %Application Data%\dclogs

(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.)

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

  • “DC_MUTEX-[0-9A-Z]{7}” where [0-9A-Z]{7} is basically a 7-character string consisting of numbers and capital letters

Autostart Technique

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

  • %User Startup%\oznz68mk.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 adds the following registry keys:

HKEY_CURRENT_USER\Software\DC3_FEXEC

Backdoor Routine

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

  • Disable RegistryTools
  • Disable TaskMgr
  • Disable Control Panel
  • List disk drives
  • List webcams and monitor/capture video
  • Change MSN Messenger status & modify contact list
  • Shutdown, Restart, Log off or Lock computer
  • Empty Recycle Bin
  • Visit arbitrary C&C servers
  • List active windows
  • Remote shell command
  • Download and execute files
  • Download updated copy of itself
  • Upload files
  • Log keystrokes
  • Refresh or delete logs
  • Modify system's host file
  • Record and play sounds
  • Open and close CD-ROM drive door
  • Steal passwords
  • Get torrent files
  • Refresh Wifi
  • Uninstall programs
  • Start and control chat sessions
  • Monitor activity by Remote Desktop Protocol
  • DDOS Flooding
  • Manipulate the following:
  • Browser
  • Clipboard
  • Desktop
  • Dialog Box
  • Files
  • Folders
  • Mouse clicks
  • Processes
  • Registries
  • Services
  • Shutdown button options
  • Start button
  • System clock
  • System tray
  • Taskbar
  • Lessen system security level by:
  • Disabling update notification
  • Disabling AV notification
  • Disabling firewall
  • Disabling services
  • Disabling LUA notification
  • Manipulate the following:
    • Browser
    • Clipboard
    • Desktop
    • Dialog Box
    • Files
    • Folders
    • Mouse clicks
    • Processes
    • Registries
    • Services
    • Shutdown button options
    • Start button
    • System clock
    • System tray
    • Taskbar
  • Lessen system security level by:
    • Disabling update notification
    • Disabling AV notification
    • Disabling firewall
    • Disabling services
    • Disabling LUA notification

It connects to the following websites to send and receive information:

  • {BLOCKED}inz.{BLOCKED}o.com:1717

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

Dropping Routine

This backdoor drops the following file(s), which it uses for its keylogging routine:

  • %Application Data%\dclogs\{YYYY-MM-DD-S}.dc ->log file

(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.)

Information Theft

This backdoor gathers the following data:

  • Admin rights
  • Computer/User name
  • Language/Country
  • Operating System information
  • RAM used
  • Web Cam information

NOTES:
The malware logs the following information:

  • Program
  • Time
  • Keystrokes

  SOLUTION

Minimum Scan Engine:

9.750

FIRST VSAPI PATTERN FILE:

11.862.09

FIRST VSAPI PATTERN DATE:

18 Aug 2015

VSAPI OPR PATTERN File:

11.863.00

VSAPI OPR PATTERN Date:

19 Aug 2015

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

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
    • DC3_FEXEC

Step 5

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.
  • %Application Data%\i9FwLiiVlr\oznz68mk.exe
  • %Application Data%\dclogs\{YYYY-MM-DD-S}.dc

Step 6

Search and delete these folders

[ 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.
  • %Application Data%\i9FwLiiVlr
  • %Application Data%\dclogs

Step 7

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