TROJ_KOVTER.YADP

 Analysis by: Cris Nowell Pantanilla

 ALIASES:

Trojan.Win32.Kovter.tcf (Kaspersky), Win32/Kovter.C (ESET-NOD32), Gen:Variant.Kovter.1 (F-Secure)

 PLATFORM:

Windows

 OVERALL RISK RATING:
 REPORTED INFECTION:

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Spammed via email

This Trojan may be downloaded by other malware/grayware/spyware from remote sites.

It connects to certain websites to send and receive information. It deletes the initially executed copy of itself.

  TECHNICAL DETAILS

File Size:

291,441 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

21 Sep 2016

Payload:

Connects to URLs/IPs

Arrival Details

This Trojan may be downloaded by other malware/grayware/spyware from remote sites.

Installation

This Trojan drops the following files:

  • %Application Data%\{random string}\{random}.lnk - link to Batch file
  • %Application Data%\{random string}\{random}.bat - starts Encrypted file
  • %Application Data%\{random string}\{random}.{random} - Encrypted file

(Note: %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 drops the following copies of itself into the affected system:

  • %Application Data%\{random string}\{random string}.exe

(Note: %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 creates the following folders:

  • %Application Data%\{random string}

(Note: %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):

  • regsvr32.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) = ""C:\WINDOWS\system32\mshta.exe" javascript:NNz6V0CG="iKaSv5Y";o7v8=new%20ActiveXObject("WScript.Shell");nlE84vzX="3c2g";qK5zB9=o7v8.RegRead("HKCU\software\{Random String 2}\{Random String 4}");Byo7Ers="TIBUOl";eval(qK5zB9);S23ZTrQx="Bym";"

HKEY_CURRENT_USER\Software\Microsoft\
Windows\CurrentVersion\Run
(Default) = ""%Application Data%\{random string}\{random}.lnk""

Other System Modifications

This Trojan adds the following registry entries as part of its installation routine:

HKEY_CLASSES_ROOT\{Random String 1}

HKEY_CURRENT_USER\Software\{Random String 2}

HKEY_CURRENT_USER\Software\{Random String 2}
{random string} = "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; .NET CLR 2.0.50727; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729; .NET4.0C; .NET4.0E; InfoPath.2)"

HKEY_CURRENT_USER\Software\{Random String 2}
{random string} = {data}

HKEY_CURRENT_USER\Software\{Random String 2}
{random string} = "%Application Data%\{random string}\{random}.exe"

HKEY_CLASSES_ROOT\{Random String 1}\shell\
open\command
(Default) = ""C:\WINDOWS\system32\mshta.exe" "javascript:Ohd3Evj="WD";ap0=new ActiveXObject("WScript.Shell");beSwO9="IUi";sZO08Q=ap0.RegRead("HKCU\software\{Random String 2}\{Random String 4}");uExW6Y5M="2";eval(sZO08Q);Iq82jsDO="d99Pmz";""

HKEY_CURRENT_USER\Software\{Random String 2}
{Random String 3} = {Encrypted Data}

HKEY_CURRENT_USER\Software\{Random String 2}
{Random String 4} = {Loader Script}

HKEY_LOCAL_MACHINE\Software\{Random String 2}

HKEY_LOCAL_MACHINE\Software\{Random String 2}
{random string} = "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; .NET CLR 2.0.50727; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729; .NET4.0C; .NET4.0E; InfoPath.2)"

HKEY_LOCAL_MACHINE\Software\{Random String 2}
{random string} = {data}

HKEY_LOCAL_MACHINE\Software\{Random String 2}
{random string} = "%Application Data%\{random string}\{random}.exe"

HKEY_LOCAL_MACHINE\Software\{Random String 2}
{Random String 3} = {Encrypted Data}

HKEY_LOCAL_MACHINE\Software\{Random String 2}
{Random String 4} = {Loader Script}

HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\Main\FeatureControl\
FEATURE_BROWSER_EMULATION
regsvr32.exe = 000022b8

HKEY_CURRENT_USER\Software\Microsoft\
Internet Explorer\Main\FeatureControl\
FEATURE_BROWSER_EMULATION
iexplore.exe = 000022b8

HKEY_LOCAL_MACHINE\Software\Microsoft\
Internet Explorer\Main\FeatureControl\
FEATURE_BROWSER_EMULATION
regsvr32.exe = 000022b8

HKEY_LOCAL_MACHINE\Software\Microsoft\
Internet Explorer\Main\FeatureControl\
FEATURE_BROWSER_EMULATION
iexplore.exe = 000022b8

Other Details

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

  • http://{BLOCKED}.{BLOCKED}.72.90/upload.php

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 the initially executed copy of itself

  SOLUTION

Minimum Scan Engine:

9.800

FIRST VSAPI PATTERN FILE:

12.790.04

FIRST VSAPI PATTERN DATE:

21 Sep 2016

VSAPI OPR PATTERN File:

12.791.00

VSAPI OPR PATTERN Date:

22 Sep 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

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_CLASSES_ROOT
    • {Random String 1}
  • In HKEY_CURRENT_USER\Software
    • {Random String 2}
  • In HKEY_LOCAL_MACHINE\Software
    • {Random String 2}

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\Internet Explorer\Main\FeatureControl\FEATURE_BROWSER_EMULATION
    • regsvr32.exe = "dword:000022b8"
  • In HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\Main\FeatureControl\FEATURE_BROWSER_EMULATION
    • iexplore.exe = "dword:000022b8"
  • In HKEY_LOCAL_MACHINE\Software\Microsoft\Internet Explorer\Main\FeatureControl\FEATURE_BROWSER_EMULATION
    • regsvr32.exe = "dword:000022b8"
  • In HKEY_LOCAL_MACHINE\Software\Microsoft\Internet Explorer\Main\FeatureControl\FEATURE_BROWSER_EMULATION
    • iexplore.exe = "dword:000022b8"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • (default) = ""C:\WINDOWS\system32\mshta.exe" javascript:NNz6V0CG="iKaSv5Y";o7v8=new%20ActiveXObject("WScript.Shell");nlE84vzX="3c2g";qK5zB9=o7v8.RegRead("HKCU\\software\\{Random String 2}\\{Random String 4}");Byo7Ers="TIBUOl";eval(qK5zB9);S23ZTrQx="Bym";"
  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • (default) = ""%Application Data%\{random string}\{random}.lnk""

Step 5

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. %Application Data%\{random string}

Step 6

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


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