BKDR_FYNLOSKI.BV

 Analysis by: Roland Marco Dela Paz

 ALIASES:

Backdoor:Win32/Fynloski.A (Microsoft)

 PLATFORM:

Windows 2000, Windows XP, Windows Server 2003

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Via instant message

This backdoor disguises as a revolutionary document in order to lure Syrian activists into downloading and executing the malware.

To get a one-glance comprehensive view of the behavior of this Backdoor, refer to the Threat Diagram shown below.

This backdoor gathers certain information on the affected system. It logs active windows and user key strokes. It is capable of executing several commands on the affected system.

This backdoor opens a hidden Internet Explorer window. It connects to a website to send and receive information.

  TECHNICAL DETAILS

File Size:

3,221,392 bytes

File Type:

Other

Memory Resident:

Yes

Initial Samples Received Date:

04 Jun 2012

Payload:

Connects to URLs/IPs, Steals information

Installation

This backdoor drops the following files:

  • %User Temp%\explorer.exe - also detected as BKDR_FYNLOSKI.BV
  • %User Temp%\Firefox.dll - encrypted component detected as BKDR_FYNLOS.ENC
  • %User Temp%\Aleppo plan.pdf - non-malicious PDF file

(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.)

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

  • DC_MUTEX-F54S21D

Autostart Technique

This backdoor drops the following file(s) in the Windows User Startup folder to enable its automatic execution at every system startup:

  • (empty).lnk

Other System Modifications

This backdoor adds the following registry keys:

HKEY_CURRENT_USER\Software\DC3_FEXEC

Backdoor Routine

This backdoor opens a hidden Internet Explorer window.

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

  • {BLOCKED}.{BLOCKED}.0.28

Stolen Information

This backdoor saves the stolen information in the following file:

  • %User Temp%\dclogs.sys

(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.)

NOTES:

This backdoor arrives as a RAR archive that is sent over Skype by a malicious user.

It gathers the following information from the affected system:

  • Administrative rights
  • Computer/User name
  • HWID
  • Language/Country
  • Operating System information
  • RAM used
  • Web cam information

It logs active windows and user key strokes.

It is capable of executing the following commands:

  • Disable notifications of antivirus software
  • Display a message box
  • Download an updated copy of itself
  • Download and execute files
  • List active windows
  • Manipulate files
  • Manipulate processes
  • Manipulate registries
  • Modify privileges
  • Modify the hosts file
  • Modify user groups
  • Monitor webcam activity
  • Open command prompt
  • Steal passwords
  • Uninstall applications
  • Uninstall itself

  SOLUTION

Minimum Scan Engine:

9.200

VSAPI OPR PATTERN File:

9.173.00

VSAPI OPR PATTERN Date:

05 Jun 2012

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

Remove malware files dropped/downloaded by BKDR_FYNLOSKI.BV

    • BKDR_FYNLOS.ENC

Step 3

Restart in Safe Mode

[ Learn More ]

Step 4

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.
  • %User Temp%\Aleppo plan.pdf
  • %User Temp%\dclogs.sys
  • %User Startup%\(empty).lnk

Step 5

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 6

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