Fileless-KOVTER

 Analysis by: John Kevin Sanchez

 THREAT SUBTYPE:

Fileless

 PLATFORM:

Windows

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: No

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Dropped by other malware, Downloaded from the Internet


This Trojan arrives on a system as a file dropped by other malware or as a file downloaded unknowingly by users when visiting malicious sites.

It modifies the Internet Explorer Zone Settings.

It connects to certain websites to send and receive information. It deletes itself after execution.

  TECHNICAL DETAILS

File Size:

291,441 bytes

Memory Resident:

Yes

Initial Samples Received Date:

21 Aug 2016

Payload:

Connects to URLs/IPs, Creates files

Arrival Details

This Trojan 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 Trojan drops the following files:

  • %AppDataLocal%\{random folder name 1}\{random filename}.{random file extension} - Encrypted file
  • %AppDataLocal%\{random folder name 1}\{random filename}.bat - starts Encrypted file
  • %AppDataLocal%\{random folder name 1}\{random filename}.lnk - starts BAT file
  • %Application Data%\{random folder name 2}\{random filename}.{random file extension} - Encrypted file
  • %User Startup%\{random filename}.lnk - Starts Encrypted file

(Note: %AppDataLocal% is the Application Data folder found in Local Settings, where it is usually C:\Documents and Settings\{user name}\Local Settings\Application Data on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local 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.. %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.. %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.)

It adds the following processes:

  • %System%\regsvr32.exe

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

It creates the following folders:

  • %AppDataLocal%\{random folder name 1}
  • %Application Data%\{random folder name 2}

(Note: %AppDataLocal% is the Application Data folder found in Local Settings, where it is usually C:\Documents and Settings\{user name}\Local Settings\Application Data on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Local 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.. %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 injects codes into the following process(es):

  • %System%\regsvr32.exe

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

Autostart Technique

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

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
{Random Value} = {Random Value} = %AppDataLocal%\{random folder name 1}\{random filename}.lnk

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
{Random Value} = "%System%\mshta.exe" "javascript:{Random}="{Random}";{Random}=new ActiveXObject("WScript.Shell");{Random}="{Random}";{Random Variable}={Random}.RegRead("HKCU\software\{Random Registry Key}\{Random Registry Value}");{Random}="{Random}";eval({Random Variable});{Random}="{Random}";"

Other System Modifications

This Trojan adds the following registry keys:

HKEY_CLASSES_ROOT\{Random Value}

HKEY_CLASSES_ROOT\.{random file extension}

HKEY_CURRENT_USER\Software\{Random Registry Key}

HKEY_CLASSES_ROOT\{Random Value}\shell

HKEY_CLASSES_ROOT\{Random Value}\shell\
open

HKEY_CLASSES_ROOT\{Random Value}\shell\
open\command

It adds the following registry entries:

HKEY_LOCAL_MACHINE\SOFTWARE\Policies\
Microsoft\Windows\WindowsUpdate
DisableOSUpgrade = 1

HKEY_LOCAL_MACHINE\SOFTWARE\Policies\
Microsoft\Windows\WindowsUpdate\
OSUpgrade
ReservationsAllowed = 0

HKEY_CLASSES_ROOT\.{random file extension}
{Default} = {Random Value}

HKEY_CLASSES_ROOT\{Random Value}\shell\
open\command
{Default} = "%System%\mshta.exe" "javascript:{Random}="{Random}";{Random}=new ActiveXObject("WScript.Shell");{Random}="{Random}";{Random Variable}={Random}.RegRead("HKCU\software\{Random Registry Key}\{Random Registry Value}");{Random}="{Random}";eval({Random Variable});{Random}="{Random}";"

HKEY_CURRENT_USER\Software\{Random Registry Key}
{Random Registry Value 2} = Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.1; Trident/4.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; Media Center PC 6.0; InfoPath.2; .NET4.0C; .NET4.0E)

HKEY_CURRENT_USER\Software\{Random Registry Key}
{Random Registry Value} = {Encrypted Data - Powershell script}

HKEY_CURRENT_USER\Software\{Random Registry Key}
{Random Registry Value 3} = {Encrypted Data - to be decrypted by PowerShell process}

HKEY_CURRENT_USER\Software\{Random Registry Key}
{Random Registry Value 4} = {Random Characters}

HKEY_CURRENT_USER\Software\{Random Registry Key}
{Random Registry Value 5} = {Random Characters}

HKEY_CURRENT_USER\Software\{Random Registry Key}
{Random Registry Value 6} = {Random Characters}

Web Browser Home Page and Search Page Modification

This Trojan modifies the Internet Explorer Zone Settings.

Other Details

This Trojan connects to the following website to send and receive information:

  • http://{blocked}5.{blocked}7.72.90/upload.php
  • http://{BLOCKED}.{BLOCKED}.67.23/upload.php
  • {Random Generated IP Address} - used for click-fraud activity

It does the following:

  • It may download and install the following software on the affected system:
    • Microsoft .Net Framework
    • Microsoft Powershell
    • Adobe Flash Player
  • Connects to certain IP address for its click-fraud activity.
  • Uses power shell to execute the obfuscated codes in the registry.

It deletes itself after execution.

NOTES:

This malware uses shell spawning techniques where it installs registry entries in Classes Root based on the random file extension of the random file in %AppDataLocal%\{random folder name 1}. When the machine restarts or either the shortcut (.LNK) or batch (.BAT) files are triggered, the execution of the random file leads to reading a malicious registry entry as shown by the registry data of the default registry value of HKEY_CLASSES_ROOT\{Random Value}\shell\open\command.

The malicious registry entry read by the shell spawning technique is usually located in HKEY_CURRENT_USER\Software\{Random Registry Key}. The decrypted registry entry contains shell code that it injects to a created PowerShell process. This shell code decrypts the registry entry located in the same random registry key. The decrypted registry entry is a binary file that it injects into a spawned process (regsvr32.exe). This spawned process would then try to connect to various URLs as a part of its click fraud activity.

  SOLUTION

Minimum Scan Engine:

9.850

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_CLASSES_ROOT
    • .{random file extension}
  • In HKEY_CLASSES_ROOT
    • {Random Value}
  • In HKEY_CURRENT_USER\Software
    • {Random Registry Key}

Step 5

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\SOFTWARE\Policies\Microsoft\Windows\WindowsUpdate
    • DisableOSUpgrade = 1
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\WindowsUpdate\OSUpgrade
    • ReservationsAllowed = 0
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • {Random Value} = %AppDataLocal%\{Random String}\{Random String}.lnk
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • {Random Value} = "%System%\mshta.exe" "javascript:{Random}="{Random}";{Random}=new ActiveXObject("WScript.Shell");{Random}="{Random}";{Random Variable}={Random}.RegRead("HKCU\software\{Random Registry Key}\{Random Registry Value}");{Random}="{Random}";eval({Random Variable});{Random}="{Random}";"

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.
  • %AppDataLocal%\{random folder name 1}
  • %Application Data%\{random folder name 2}

Step 7

Search and delete these files

[ 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 Startup%\{random filename}.lnk

Step 8

Restart in normal mode and scan your computer with your Trend Micro product for files detected as Fileless-KOVTER. 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 9

Reset Internet security settings

[ Learn More ]


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