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LNK_KOVTER.SM

July 13, 2017
 Analysis by: Johnlery Triunfante
 ALIASES:

Exploit.Poweliks.Gen.3 (BITDEFENDER)

 PLATFORM:

Windows

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

  • Threat Type: Trojan

  • Destructiveness: No

  • Encrypted: Yes

  • In the wild: Yes

  OVERVIEW

Infection Channel:

Dropped by other malware


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

  TECHNICAL DETAILS

File Size:

1,033 bytes

File Type:

LNK

Memory Resident:

Yes

Initial Samples Received Date:

11 Jul 2017

Payload:

Drops 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.

It 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 extension 1} - Encrypted file
  • %Start Menu%\Programs\Startup\{random}.lnk

(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.. %Start Menu% is the Start Menu folder, where it usually is C:\Documents and Settings\{user name}\Start Menu on Windows 2000, Windows Server 2003, and Windows XP (32- and 64-bit); C:\Users\{user name}\AppData\Roaming\Microsoft\Windows\Start Menu 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.)

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) = %Application Data%\{random string}\{random}.bat

Other System Modifications

This Trojan adds the following registry entries:

HKEY_CLASSES_ROOT\.{random extension 1}
(Default) = "{random value 1}"

HKEY_CLASSES_ROOT\{random value 1}\shell\
open\command
(Default) = mshta \"about:(script){variable 1}=\"s5KE\";{variable 2}=new ActiveXObject(\"WScript.Shell\");{variable 3}=\"oepop\";{variable 4}={variable 2}.RegRead(\"HKCU\\software\\{random string 1}\\{name 2}\");{variable 5}=\"Ijwl\";eval({variable 4});{variable 6}=\"nb2Wjac\";(/script)\""

HKEY_CURRENT_USER\Software\{random string 1}
{multiple registry name} = "{multiple encrypted data}"

Other Details

This Trojan does the following:

  • It executes the following command:
    • start "random string" "%LOCALAPPDATA%\{random}\{random}.{random}"

  SOLUTION

Minimum Scan Engine:

9.850

FIRST VSAPI PATTERN FILE:

13.514.05

FIRST VSAPI PATTERN DATE:

05 Jul 2017

VSAPI OPR PATTERN File:

13.515.00

VSAPI OPR PATTERN Date:

06 Jul 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.

  • In HKEY_CLASSES_ROOT
    • .{random extension 1}
  • In HKEY_CURRENT_USER\Software
    • {random string 1}
  • In HKEY_CLASSES_ROOT
    • {random value 1}

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) = %Application Data%\{random string}\{random}.bat

Step 6

Search and delete this folder

[ 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 7

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