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TROJ_KOVTER.AUSKKM

October 12, 2017
 Analysis by: Rheniel Rhay Ramos
 ALIASES:

Trojan.Win32.Kovter.nfm (Kaspersky); Trojan:Win32/Kovter.I (Microsoft); Trojan.Kovter (Malwarebytes)

 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:

218,039 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

05 Oct 2017

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 String}\{Random}lnk
  • %AppDataLocal%\{Random String}\{Random String}.exe -> Slightly modified Copy
  • %AppDataLocal%\{Random String}\{Random String}.{Random Extension} - Encrypted file
  • %AppDataLocal%\{Random String}\{Random}.bat - 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.)

It adds the following processes:

  • explorer.exe

It creates the following folders:

  • %AppDataLocal%\{Random String}

(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.)

It injects codes into the following process(es):

  • explorer.exe

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

HKEY_CURRENT_USER\Software\Classes\
{Random String}\shell\open\
command
(Default) = "%System%\mshta.exe" "javascript:{Random}="{Random}";{Random}=new ActiveXObject("WScript.Shell");{Random}="{Random}";{Random}={Random}.RegRead("HKCU\software\{Random String 2}\{Random Value Name}");{Random}="{Random}";eval({Random});{Random}="{Random}";"

Other System Modifications

This Trojan adds the following registry keys:

HKEY_CURRENT_USER\Software\Classes\
{Random String}

HKEY_CURRENT_USER\Software\{Random String 1}

HKEY_CURRENT_USER\Software\{Random String 2}

HKEY_LOCAL_MACHINE\Software\{Random String 2}

HKEY_CURRENT_USER\Software\Classes\
.{Random Extension}

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_LOCAL_MACHINE\SOFTWARE\{Random String 2}
{Random Value Name 1} = {Encrypted Data}

HKEY_LOCAL_MACHINE\SOFTWARE\{Random String 2}
{Random Value Name 2} = {Random Characters}

HKEY_LOCAL_MACHINE\SOFTWARE\{Random String 2}
{Random Value Name 3} = {Random Characters}

HKEY_LOCAL_MACHINE\SOFTWARE\{Random String 2}
{Random Value Name 4} = {Random Characters}

HKEY_LOCAL_MACHINE\SOFTWARE\{Random String 2}
{Random Value Name 5} = {Random Characters}

HKEY_LOCAL_MACHINE\SOFTWARE\{Random String 2}
{Random Value Name 6} = {Random Characters}

HKEY_CURRENT_USER\SOFTWARE\{Random String 2}
{Random Value Name 1} = {Encrypted Data}

HKEY_CURRENT_USER\SOFTWARE\{Random String 2}
{Random Value Name 2} = {Random Characters}

HKEY_CURRENT_USER\SOFTWARE\{Random String 2}
{Random Value Name 3} = {Random Characters}

HKEY_CURRENT_USER\SOFTWARE\{Random String 2}
{Random Value Name 4} = {Random Characters}

HKEY_CURRENT_USER\SOFTWARE\{Random String 2}
{Random Value Name 5} = {Random Characters}

HKEY_CURRENT_USER\SOFTWARE\{Random String 2}
{Random Value Name 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}.67.16/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:

13.710.03

FIRST VSAPI PATTERN DATE:

05 Oct 2017

VSAPI OPR PATTERN File:

13.711.00

VSAPI OPR PATTERN Date:

06 Oct 2017

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.

  • HKEY_CURRENT_USER\Software\{Random String 1}
  • HKEY_CURRENT_USER\Software\{Random String 2}
  • HKEY_LOCAL_MACHINE\Software\{Random String 2}
  • HKEY_CURRENT_USER\Software\Classes\.{Random Extension}
  • HKEY_CURRENT_USER\Software\Classes\{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_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • (Default) = %AppDataLocal%\{Random String}\{Random String}.lnk
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\WindowsUpdate
    • DisableOSUpgrade = 1
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\WindowsUpdate\OSUpgrade
    • ReservationsAllowed = 0

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 String}

Step 7

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

Reset Internet security settings

[ Learn More ]


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