BKDR_TOFSEE.BYX

July 05, 2016
 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.

It deletes itself after execution.

  TECHNICAL DETAILS

File Size:

151,552 bytes

File Type:

EXE

Memory Resident:

No

Initial Samples Received Date:

05 Jul 2016

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 adds the following registry entries to enable its automatic execution at every system startup:

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
MSConfig = "%User Profile%\yyhhvgtt.exe "

Other System Modifications

This backdoor deletes the following files:

  • %System Root%\log_plg_antibot.txt
  • %System Root%\log_plg_proxy.txt
  • %User Temp%\log_plg_proxy.txt
  • %System Root%\log_plg_webm.txt
  • %User Temp%\log_plg_webm.txt
  • %System Root%\log_plg_locs.txt
  • %System Root%\log_plg_host2.txt
  • %User Temp%\log_plg_host2.txt
  • %System Root%\log_plg_text.txt
  • %User Temp%\log_plg_text.txt
  • %System Root%\log_plg_smtp.txt
  • %User Temp%\log_plg_smtp.txt
  • %System Root%\log_plg_blist.txt
  • %User Temp%\log_plg_blist.txt
  • %System Root%\log_plg_miner.txt
  • %User Temp%\log_plg_miner.txt
  • %System Root%\log_plg_img.txt
  • %User Temp%\log_plg_img.txt
  • %System Root%\log_plg_spread1.txt
  • %User Temp%\log_plg_spread1.txt
  • %System Root%\log_plg_spread2.txt
  • %User Temp%\log_plg_spread2.txt
  • %System Root%\log_plg_sys.txt
  • %User Temp%\log_plg_sys.txt
  • %System Root%\log_plg_webb.txt
  • %User Temp%\log_plg_webb.txt
  • %System Root%\log_plg_p2p.txt
  • %User Temp%\log_plg_p2p.txt
  • %Program Files%\Common Files\Adobe\Acrobat\ActiveX\AcroIEHelperShim.dll

(Note: %System Root% is the Windows root folder, where it usually is C:\ on all Windows operating system versions.. %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.. %Program Files% is the Program Files folder, where it usually is C:\Program Files on all Windows operating system versions; C:\Program Files (x86) for 32-bit applications running on Windows 64-bit operating systems.)

It adds the following registry keys:

HKEY_CURRENT_USER\SOFTWARE\Microsoft\
DeviceControl

HKEY_CURRENT_USER\Software\WinRAR

It adds the following registry entries:

HKEY_CURRENT_USER\Software\Microsoft\
DeviceControl
DevData0 = "{random values}"

HKEY_CURRENT_USER\Software\Microsoft\
DeviceControl
DevData1 = "{random values}"

HKEY_CURRENT_USER\Software\Microsoft\
DeviceControl
DevData2 = "{random values}"

HKEY_CURRENT_USER\Software\Microsoft\
DeviceControl
DevData3 = "{random values}"

HKEY_CURRENT_USER\Software\WinRAR
HWID = "{random values}"

It modifies the following registry entries:

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\Eventlog\Application\
ESENT
EventMessageFile = "%System%\ESENT.dll"

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

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\Eventlog\Application\
ESENT
CategoryMessageFile = "%System%\ESENT.dll"

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

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\Eventlog\Application\
ESENT
CategoryCount = "1"

(Note: The default value data of the said registry entry is 10.)

HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\
Services\Eventlog\Application\
ESENT
TypesSupported = "7"

(Note: The default value data of the said registry entry is 7.)

It deletes the following registry keys:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\
Windows\CurrentVersion\Explorer\
Browser Helper Objects\{18DF081C-E8AD-4283-A596-FA578C2EBDC3}

HKEY_CLASSES_ROOT\CLSID\{18DF081C-E8AD-4283-A596-FA578C2EBDC3}\
InprocServer32

HKEY_CLASSES_ROOT\CLSID\{18DF081C-E8AD-4283-A596-FA578C2EBDC3}\
ProgID

HKEY_CLASSES_ROOT\CLSID\{18DF081C-E8AD-4283-A596-FA578C2EBDC3}\
Programmable

HKEY_CLASSES_ROOT\CLSID\{18DF081C-E8AD-4283-A596-FA578C2EBDC3}\
TypeLib

HKEY_CLASSES_ROOT\CLSID\{18DF081C-E8AD-4283-A596-FA578C2EBDC3}\
VersionIndependentProgID

HKEY_CLASSES_ROOT\CLSID\{18DF081C-E8AD-4283-A596-FA578C2EBDC3}

Dropping Routine

This backdoor drops the following files:

  • %User Profile%\yyhhvgtt.exe
  • %User Profile%\Local Settings:init
  • %User Temp%\HWID
  • %User Temp%\01868.tmp

(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.. %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}1.193.242
  • {BLOCKED}4.91.76
  • {BLOCKED}.137.79
  • {BLOCKED}.112.32
  • {BLOCKED}0.2.199
  • {BLOCKED}.232.11
  • {BLOCKED}0.159.21
  • {BLOCKED}188.126
  • {BLOCKED}.118.36
  • {BLOCKED}.8.199
  • {BLOCKED}3.0.68
  • {BLOCKED}.182.27
  • {BLOCKED}3.0.67
  • {BLOCKED}.192.45
  • {BLOCKED}37.120
  • {BLOCKED}.192.27
  • {BLOCKED}.8.167
  • {BLOCKED}.186.150
  • {BLOCKED}.0.77
  • {BLOCKED}229.72
  • {BLOCKED}2.252.75
  • {BLOCKED}81.57
  • {BLOCKED}26.145
  • {BLOCKED}.62.201
  • {BLOCKED}91.113
  • {BLOCKED}.195.228
  • {BLOCKED}.34.86
  • {BLOCKED}.255.133
  • {BLOCKED}1.216.108

It deletes itself after execution.

This report is generated via an automated analysis system.

  SOLUTION

Minimum Scan Engine:

9.8

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\Microsoft
    • DeviceControl
  • In HKEY_CURRENT_USER\Software
    • WinRAR

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
    • MSConfig = "%User Profile%\yyhhvgtt.exe "
  • In HKEY_CURRENT_USER\Software\Microsoft\DeviceControl
    • DevData0 = "{random values}"
  • In HKEY_CURRENT_USER\Software\Microsoft\DeviceControl
    • DevData1 = "{random values}"
  • In HKEY_CURRENT_USER\Software\Microsoft\DeviceControl
    • DevData2 = "{random values}"
  • In HKEY_CURRENT_USER\Software\Microsoft\DeviceControl
    • DevData3 = "{random values}"
  • In HKEY_CURRENT_USER\Software\WinRAR
    • HWID = "{random values}"

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\SYSTEM\ControlSet001\Services\Eventlog\Application\ESENT
    • From: EventMessageFile = "%System%\ESENT.dll"
      To: EventMessageFile = ""{random values}""
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\Eventlog\Application\ESENT
    • From: CategoryMessageFile = "%System%\ESENT.dll"
      To: CategoryMessageFile = ""{random values}""
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\Eventlog\Application\ESENT
    • From: CategoryCount = "1"
      To: CategoryCount = ""10""
  • In HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Services\Eventlog\Application\ESENT
    • From: TypesSupported = "7"
      To: TypesSupported = ""7""

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 Profile%\yyhhvgtt.exe
  • %User Profile%\Local Settings:init
  • %User Temp%\HWID
  • %User Temp%\01868.tmp

Step 7

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

  • %System Root%\log_plg_antibot.txt
  • %System Root%\log_plg_proxy.txt
  • %User Temp%\log_plg_proxy.txt
  • %System Root%\log_plg_webm.txt
  • %User Temp%\log_plg_webm.txt
  • %System Root%\log_plg_locs.txt
  • %System Root%\log_plg_host2.txt
  • %User Temp%\log_plg_host2.txt
  • %System Root%\log_plg_text.txt
  • %User Temp%\log_plg_text.txt
  • %System Root%\log_plg_smtp.txt
  • %User Temp%\log_plg_smtp.txt
  • %System Root%\log_plg_blist.txt
  • %User Temp%\log_plg_blist.txt
  • %System Root%\log_plg_miner.txt
  • %User Temp%\log_plg_miner.txt
  • %System Root%\log_plg_img.txt
  • %User Temp%\log_plg_img.txt
  • %System Root%\log_plg_spread1.txt
  • %User Temp%\log_plg_spread1.txt
  • %System Root%\log_plg_spread2.txt
  • %User Temp%\log_plg_spread2.txt
  • %System Root%\log_plg_sys.txt
  • %User Temp%\log_plg_sys.txt
  • %System Root%\log_plg_webb.txt
  • %User Temp%\log_plg_webb.txt
  • %System Root%\log_plg_p2p.txt
  • %User Temp%\log_plg_p2p.txt
  • %Program Files%\Common Files\Adobe\Acrobat\ActiveX\AcroIEHelperShim.dll

Step 9

Restore these deleted registry keys/values from backup

*Note: Only Microsoft-related keys/values will be restored. If the malware/grayware also deleted registry keys/values related to programs that are not from Microsoft, please reinstall those programs on your computer.

  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Browser Helper Objects
    • {18DF081C-E8AD-4283-A596-FA578C2EBDC3}
  • In HKEY_CLASSES_ROOT\CLSID\{18DF081C-E8AD-4283-A596-FA578C2EBDC3}
    • InprocServer32
  • In HKEY_CLASSES_ROOT\CLSID\{18DF081C-E8AD-4283-A596-FA578C2EBDC3}
    • ProgID
  • In HKEY_CLASSES_ROOT\CLSID\{18DF081C-E8AD-4283-A596-FA578C2EBDC3}
    • Programmable
  • In HKEY_CLASSES_ROOT\CLSID\{18DF081C-E8AD-4283-A596-FA578C2EBDC3}
    • TypeLib
  • In HKEY_CLASSES_ROOT\CLSID\{18DF081C-E8AD-4283-A596-FA578C2EBDC3}
    • VersionIndependentProgID
  • In HKEY_CLASSES_ROOT\CLSID
    • {18DF081C-E8AD-4283-A596-FA578C2EBDC3}


Did this description help? Tell us how we did.