Analysis by: John Kevin Sanchez

ALIASES:

Trojan:Win32/Kovter (Microsoft), Trojan.Win32.Kovter.nwt (Kaspersky), Trojan.Kovter (VBA32)

 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: 337,152 bytes
File Type: EXE
Memory Resident: Yes
Initial Samples Received Date: 09 Jun 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}\{random filename}.{random file extension} - Encrypted file
  • %AppDataLocal%\{random folder name}\{random filename}.bat - starts Encrypted file
  • %AppDataLocal%\{random folder name}\{random filename}.lnk - starts BAT file
  • %Application Data%\{random folder name}\{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}
  • %Application Data%\{random folder name}

(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} = %AppDataLocal%\{Random String}\{Random String}.lnk

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
{Random Value} = "%System%\mshta.exe" "javascript:{Random}="{Random}";{Random Variable}=new ActiveXObject("WScript.Shell");{Random}="{Random}";EKb5F=Rq55.RegRead("HKCU\software\{Random String 2}\{Random Value Name}");{Random}="{Random}";eval({Random Variable});{Random}="{Random}";"

Other System Modifications

This Trojan adds the following registry keys:

HKEY_CLASSES_ROOT\{Random String}

HKEY_CLASSES_ROOT\.{Random File Extension}

HKEY_CURRENT_USER\Software\{Random String}

HKEY_CLASSES_ROOT\{Random String}\shell

HKEY_CLASSES_ROOT\{Random String}\shell\
open

HKEY_CLASSES_ROOT\{Random String}\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 String}

HKEY_CLASSES_ROOT\{Random String}\shell\
open\command
{Default} = "%System%\mshta.exe" "javascript:{Random}="{Random}";{Random Variable}=new ActiveXObject("WScript.Shell");{Random}="{Random}";EKb5F=Rq55.RegRead("HKCU\software\{Random String}\{Random String 3}");{Random}="{Random}";eval({Random Variable});{Random}="{Random}";"

HKEY_CURRENT_USER\Software\{Random String}
{Random String 1} = 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 String}
{Random String 2} = {Random Characters}

HKEY_CURRENT_USER\Software\{Random String}
{Random String 3} = {Encrypted Data}

HKEY_CURRENT_USER\Software\{Random String}
{Random String 4} = {Random Characters}

HKEY_CURRENT_USER\Software\{Random String}
{Random String 5} = {Random Characters}

HKEY_CURRENT_USER\Software\{Random String}
{Random String 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}.{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 javascript codes in the registry.

It deletes itself after execution.

  SOLUTION

Minimum Scan Engine: 9.850
FIRST VSAPI PATTERN FILE: 12.828.08
FIRST VSAPI PATTERN DATE: 10 Oct 2016
VSAPI OPR PATTERN File: 12.829.00
VSAPI OPR PATTERN Date: 11 Oct 2016

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 String}
  • In HKEY_CLASSES_ROOT
    • .{Random File Extension}
  • In HKEY_CURRENT_USER\Software
    • {Random String}

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\{Random String}
    • {Random String 3} = {Encrypted Data}
  • 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 Variable}=new ActiveXObject("WScript.Shell");{Random}="{Random}";EKb5F=Rq55.RegRead("HKCU\software\{Random String 2}\{Random Value Name}");{Random}="{Random}";eval({Random Variable});{Random}="{Random}";"
  • In HKEY_CURRENT_USER\Software\Classes\{Random String}\shell\open\command
    • (Default) = "%System%\mshta.exe" "javascript:{Random}="{Random}";{Random Variable}=new ActiveXObject("WScript.Shell");{Random}="{Random}";EKb5F=Rq55.RegRead("HKCU\software\{Random String 2}\{Random Value Name}");{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}
  • %Application Data%\{random folder name}

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 TROJ_KOVTER.SMFD. 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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