BKDR_FYNLOS.WIO


 ALIASES:

TrojanDropper:Win32/Dimnie.A (Microsoft); [0001513c.EXE]:Generic-FAVQ!DD4CDE7F9991 (McAfee); Trojan.Win32.Yakes.jgoi (Kaspersky); Troj/Agent-ALSF (Sophos); Trojan.Win32.Generic!BT (Sunbelt); Found Luhe.Fiha.A.dropper (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:

593,850 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

07 Mar 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.

Autostart Technique

This backdoor registers as a system service to ensure its automatic execution at every system startup by adding the following registry keys:

HKEY_LOCAL_MACHINE\System\CurrentControlSet\
Services\AcwFiu

HKEY_LOCAL_MACHINE\System\CurrentControlSet\
Services\AcwFiu\Parameters

Other System Modifications

This backdoor deletes the following files:

  • %User Temp%\1702~1.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 adds the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\AcwFiu
ImagePath = "%SystemRoot%\System32\svchost.exe -k netsvcs"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\AcwFiu
ObjectName = "LocalSystem"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\AcwFiu
DisplayName = "AcwFiu"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\AcwFiu
Start = "2"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\AcwFiu
ErrorControl = "0"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\AcwFiu
Type = "2"

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\AcwFiu
Description = "Provides performance notifications Telephony files IP ability."

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\AcwFiu\Parameters
ServiceDll = "%System%\xnlisop.dll"

It modifies the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows NT\CurrentVersion\SvcHost
netsvcs = "{random characters}"

(Note: The default value data of the said registry entry is {random values}.)

Dropping Routine

This backdoor drops the following files:

  • %User Temp%\names.txt
  • %User Temp%\17.02.exe
  • %User Temp%\tn.jpg
  • %System%\xnlisop.dll

(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.. %System% is the Windows system folder, where it usually is C:\Windows\System32 on all Windows operating system versions.)

Other Details

This backdoor connects to the following possibly malicious URL:

  • {BLOCKED}.3.180

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine:

9.700

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_LOCAL_MACHINE\System\CurrentControlSet\Services
    • AcwFiu
  • In HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\AcwFiu
    • Parameters

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_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\AcwFiu
    • ImagePath = "%SystemRoot%\System32\svchost.exe -k netsvcs"
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\AcwFiu
    • ObjectName = "LocalSystem"
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\AcwFiu
    • DisplayName = "AcwFiu"
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\AcwFiu
    • Start = "2"
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\AcwFiu
    • ErrorControl = "0"
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\AcwFiu
    • Type = "2"
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\AcwFiu
    • Description = "Provides performance notifications Telephony files IP ability."
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\AcwFiu\Parameters
    • ServiceDll = "%System%\xnlisop.dll"

Step 5

Restore these modified registry values

[ Learn More ]

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_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\SvcHost
    • From: netsvcs = "{random characters}"
      To: netsvcs = ""{random values}""

Step 6

Search and delete these components

[ Learn More ]
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 Temp%\names.txt
  • %User Temp%\17.02.exe
  • %User Temp%\tn.jpg
  • %System%\xnlisop.dll

Step 7

Restart in normal mode and scan your computer with your Trend Micro product for files detected as BKDR_FYNLOS.WIO. 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 8

Restore this file from backup only Microsoft-related files will be restored. If this malware/grayware also deleted files related to programs that are not from Microsoft, please reinstall those programs on you computer again.

  • %User Temp%\1702~1.EXE


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