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Published Feb 27, 2018 | Updated Mar 28, 2018

Trojan:Win32/Powessere.H

Detected by Microsoft Defender Antivirus

Aliases: No associated aliases

Summary

This trojan is malicious behavior associated with Kovter and other sophisticated fileless malware.

Microsoft Defender Antivirus detects this trojan whenever a command line designed to launch certain malicious JavaScript or VBScript code is run. Microsoft Defender Antivirus blocks the execution of the malicious script code, curtailing intended fileless attack activity.

Microsoft Defender Antivirus automatically removes threats as they are detected. However, many infections can leave remnant files and system changes. Updating your antimalware definitions and running a full scan might help address these remnant artifacts.

You can also visit our advanced troubleshooting page or search the Microsoft virus and malware community for more help.

Fix redetection of this threat

If this trojan is continually redetected, especially during startup, consider checking for remnant malware entries in the registry.

NOTE: Only advanced users should modify the registry. Always back up registry entries before modifying them.

  1. Check the Microsoft Defender Antivirus detection log for the detected command line. Here is an example of the detection log:

NOTE: mshta.exe is a legitimate system file used to launch script code.

  1. Use Registry Editor to search for and remove autostart entries that run the detected command line. Most autostart entries are located in the following keys:
  • HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunServicesOnce
  • HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunServices
  • HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\RunOnce
  • HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Run
  • HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run 
  • HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\RunOnce
Secure configuration

To get the best and fastest protection from Microsoft Defender Antivirus, ensure it can connect to the cloud protection service.

Use the Windows search box to find and open the Windows Defender Security Center. Navigate to Virus & threat protection settings and enable the following:

  • Cloud-delivered protection
  • Automatic sample submission
Prevent malware infection

Refer to our guide on how to prevent malware infection.

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