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BKDR_FYNLOS.WIQ

May 12, 2015
 ALIASES:

Backdoor:Win32/Fynloski.A (Microsoft); Trojan.Win32.Reconyc.dxte (Kaspersky); Mal/Generic-L (Sophos); Trojan.Win32.Generic!BT (Sunbelt); Trojan horse Pakes2_c.AFTZ (AVG)

 PLATFORM:

Windows

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

  • Threat Type: Backdoor

  • Destructiveness: No

  • Encrypted:

  • 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.

  TECHNICAL DETAILS

File Size:

1,662,464 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

12 May 2015

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 Temp%\svchost\svchost.exe

(Note: %User Temp% is the user's temporary folder, where it usually is C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local\Temp 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:

  • %User Temp%\svchost
  • %User Profile%\Application Data\dclogs

(Note: %User Temp% is the user's temporary folder, where it usually is C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local\Temp 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.. %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
Microsoft = "%User Temp%\svchost\svchost.exe"

Other System Modifications

This backdoor adds the following registry keys:

HKEY_CURRENT_USER\Software\DC3_FEXEC

It adds the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
Windows NT\CurrentVersion\Winlogon
shell = "%User Temp%\svchost\svchost.exe,explorer.exe"

HKEY_CURRENT_USER\Software\DC3_FEXEC
3/29/2015 at 11:50:42 PM = "{1c6961c0-f82d-11e0-a6bd-806d6172696f-1756172240}"

HKEY_CURRENT_USER\Software\DC3_FEXEC
3/29/2015 at 11:50:47 PM = "{1c6961c0-f82d-11e0-a6bd-806d6172696f-1756172240}"

HKEY_CURRENT_USER\Software\DC3_FEXEC
3/29/2015 at 11:51:01 PM = "{1c6961c0-f82d-11e0-a6bd-806d6172696f-1756172240}"

HKEY_CURRENT_USER\Software\DC3_FEXEC
3/29/2015 at 11:51:16 PM = "{1c6961c0-f82d-11e0-a6bd-806d6172696f-1756172240}"

HKEY_CURRENT_USER\Software\DC3_FEXEC
3/29/2015 at 11:51:23 PM = "{1c6961c0-f82d-11e0-a6bd-806d6172696f-1756172240}"

HKEY_CURRENT_USER\Software\DC3_FEXEC
3/29/2015 at 11:51:34 PM = "{1c6961c0-f82d-11e0-a6bd-806d6172696f-1756172240}"

HKEY_CURRENT_USER\Software\DC3_FEXEC
3/29/2015 at 11:51:49 PM = "{1c6961c0-f82d-11e0-a6bd-806d6172696f-1756172240}"

HKEY_CURRENT_USER\Software\DC3_FEXEC
3/29/2015 at 11:51:56 PM = "{1c6961c0-f82d-11e0-a6bd-806d6172696f-1756172240}"

HKEY_CURRENT_USER\Software\DC3_FEXEC
3/29/2015 at 11:52:09 PM = "{1c6961c0-f82d-11e0-a6bd-806d6172696f-1756172240}"

HKEY_CURRENT_USER\Software\DC3_FEXEC
3/29/2015 at 11:52:19 PM = "{1c6961c0-f82d-11e0-a6bd-806d6172696f-1756172240}"

HKEY_CURRENT_USER\Software\DC3_FEXEC
3/29/2015 at 11:52:29 PM = "{1c6961c0-f82d-11e0-a6bd-806d6172696f-1756172240}"

HKEY_CURRENT_USER\Software\DC3_FEXEC
3/29/2015 at 11:52:40 PM = "{1c6961c0-f82d-11e0-a6bd-806d6172696f-1756172240}"

Dropping Routine

This backdoor drops the following files:

  • %User Temp%\run.vbs

(Note: %User Temp% is the user's temporary folder, where it usually is C:\Documents and Settings\{user name}\Local Settings\Temp on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local\Temp 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.)

Other Details

This backdoor connects to the following possibly malicious URL:

  • {BLOCKED}.116.186

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine:

9.750

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

Restart in Safe Mode

[ Learn More ]

Step 3

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 4

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\Run
    • Microsoft = "%User Temp%\svchost\svchost.exe"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\Winlogon
    • shell = "%User Temp%\svchost\svchost.exe,explorer.exe"
  • In HKEY_CURRENT_USER\Software\DC3_FEXEC
    • 3/29/2015 at 11:50:42 PM = "{1c6961c0-f82d-11e0-a6bd-806d6172696f-1756172240}"
  • In HKEY_CURRENT_USER\Software\DC3_FEXEC
    • 3/29/2015 at 11:50:47 PM = "{1c6961c0-f82d-11e0-a6bd-806d6172696f-1756172240}"
  • In HKEY_CURRENT_USER\Software\DC3_FEXEC
    • 3/29/2015 at 11:51:01 PM = "{1c6961c0-f82d-11e0-a6bd-806d6172696f-1756172240}"
  • In HKEY_CURRENT_USER\Software\DC3_FEXEC
    • 3/29/2015 at 11:51:16 PM = "{1c6961c0-f82d-11e0-a6bd-806d6172696f-1756172240}"
  • In HKEY_CURRENT_USER\Software\DC3_FEXEC
    • 3/29/2015 at 11:51:23 PM = "{1c6961c0-f82d-11e0-a6bd-806d6172696f-1756172240}"
  • In HKEY_CURRENT_USER\Software\DC3_FEXEC
    • 3/29/2015 at 11:51:34 PM = "{1c6961c0-f82d-11e0-a6bd-806d6172696f-1756172240}"
  • In HKEY_CURRENT_USER\Software\DC3_FEXEC
    • 3/29/2015 at 11:51:49 PM = "{1c6961c0-f82d-11e0-a6bd-806d6172696f-1756172240}"
  • In HKEY_CURRENT_USER\Software\DC3_FEXEC
    • 3/29/2015 at 11:51:56 PM = "{1c6961c0-f82d-11e0-a6bd-806d6172696f-1756172240}"
  • In HKEY_CURRENT_USER\Software\DC3_FEXEC
    • 3/29/2015 at 11:52:09 PM = "{1c6961c0-f82d-11e0-a6bd-806d6172696f-1756172240}"
  • In HKEY_CURRENT_USER\Software\DC3_FEXEC
    • 3/29/2015 at 11:52:19 PM = "{1c6961c0-f82d-11e0-a6bd-806d6172696f-1756172240}"
  • In HKEY_CURRENT_USER\Software\DC3_FEXEC
    • 3/29/2015 at 11:52:29 PM = "{1c6961c0-f82d-11e0-a6bd-806d6172696f-1756172240}"
  • In HKEY_CURRENT_USER\Software\DC3_FEXEC
    • 3/29/2015 at 11:52:40 PM = "{1c6961c0-f82d-11e0-a6bd-806d6172696f-1756172240}"

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.
  • %User Temp%\run.vbs

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.
  • %User Temp%\svchost
  • %User Profile%\Application Data\dclogs

Step 7

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