Avast Antivirus: Troubleshooting when Avast Antivirus components no longer work properly

How to troubleshoot an issue with Avast program components

One or more Avast Antivirus program components (such as the shields or Firewall) may display the STOPPED status and cannot be started manually via the Avast Antivirus user interface.

This is usually caused by limited or inconsistent permissions to write to disk, system folders, or Windows registry, which prevents Avast Setup from installing, updating, deleting, or overwriting some of its program files and/or registry entries. If any of these files/entries are corrupted or missing, it may result in the malfunction of Avast Antivirus, or some of its components.

Although some of the steps in this article may require the advanced technical knowledge, performing them is necessary to fully resolve the Avast component issues and prevent them from happening in the future.

Follow these troubleshooting steps according to your version of Windows:

Before proceeding with the troubleshooting steps, ensure that you are logged into Windows as a user with administrator permissions, and all other programs in Windows are closed.
  1. Uninstall Avast Antivirus from the system using the Avast Uninstall Utility as described in the following article:
  2. Manually delete any remaining Avast folders in the following default locations:

    64 bit type/version:
    • C:\Program Files (x86)\Avast Software or C:\Program Files (x86)\Alwil Software
    • C:\ProgramData\Avast Software or C:\ProgramData\Alwil Software


    32 bit type/version:
    • C:\Program Files\Avast Software or C:\Program Files\Alwil Software
    • C:\ProgramData\Avast Software or C:\ProgramData\Alwil Software
    Depending on your system preferences, the folders referenced above could be hidden. To display hidden files and folders in Windows 10, visit the following article and click the section entitled Look for the files using Search:
  3. Manually uninstall Avast Firewall Driver (or Avast Firewall NDIS Filter Driver) if it exists in the Properties of your Network connections, by following the steps below:
    1. In File Explorer, right-click the Network icon on the left panel, and select Properties from the context menu to open Network and Sharing Center.
    2. Click Change adapter settings in the left panel to open Network connections.
    3. Right-click one of your connection icons (for example, Local Area Connection) and select Properties from the context menu.
  4. Reboot your computer and start Windows in Safe Mode by following the instructions on the Microsoft website:
  5. In Windows Safe Mode, search and delete all files starting with aswNdis*.* if any exist in the following folder and its subfolders:
    • C:\Windows\System32\DriverStore
  6. If Windows (started in Safe Mode) refuses to delete any of these files, take ownership of the files as follows:
    1. In File Explorer, right-click the file that you want to take ownership of, then click Properties from the context menu.
    2. Click the Security tab, and then click Advanced.
    3. Next to Owner on the top, click Change (if prompted by the User Account Control dialog for permission click Yes).
    4. Type Administrator or Administrators into the field entitled Enter the object name to select, click Check Names to verify, then click OK repeatedly until all opened dialogs are closed.
  7. Clear all offline content and cookies from your web browser by following the instructions available on its vendor's website:

    Internet Explorer: Offline content/Cookies

    Mozilla Firefox: Offline content/Cookies

    Google Chrome: Offline content/Cookies

  8. Temporarily turn off any firewall software. If you are using Windows Firewall, follow the instructions on the Microsoft website:
  9. Download and install the latest version of Avast Antivirus. For detailed installation instructions, read the following article:
  10. Insert your license into Avast Antivirus. For detailed activation instructions, read the following article:
  11. If you don't have Avast Premier or Avast Internet Security which include a built-in firewall, turn on your firewall software. For more instructions, refer to the relevant vendor documentation. If you are using Windows Firewall, follow the instructions on the Microsoft website:
  1. Uninstall Avast Antivirus from the system using the Avast Uninstall Utility as described in the following article:
  2. Manually delete any remaining Avast folders in the following default locations:

    64 bit type/version:
    • C:\Program Files (x86)\Avast Software or C:\Program Files (x86)\Alwil Software
    • C:\ProgramData\Avast Software or C:\ProgramData\Alwil Software


    32 bit type/version:
    • C:\Program Files\Avast Software or C:\Program Files\Alwil Software
    • C:\ProgramData\Avast Software or C:\ProgramData\Alwil Software
    Depending on your system preferences, the folders referenced above could be hidden. To display hidden files and folders in Windows 8, visit the following article and scroll down to the section entitled Change the view:
  3. Manually uninstall Avast Firewall Driver (or Avast Firewall NDIS Filter Driver) if it exists in the Properties of your Network connections, by following these steps:
    1. In File Explorer, right-click the Network icon on the left pane, and select Properties from the context menu to open Network and Sharing Center.
    2. In Network and Sharing Center, click Change adapter settings in the left pane to open Network connections.
    3. In Network connections, right-click one of your connection icons (for example, Local Area Connection) and select Properties from the context menu.
  4. Reboot your computer and start Windows in Safe Mode by following the instructions on the Microsoft website:
  5. In Windows Safe Mode, search and delete all files starting with aswNdis*.* if any exist in the following folder and its subfolders:
    • C:\Windows\System32\DriverStore
  6. If Windows (started in Safe Mode) refuses to delete any of these files, take ownership of the files as follows:
    1. In File Explorer, right-click the file that you want to take ownership of, then click Properties from the context menu.
    2. Click the Security tab, and then click Advanced.
    3. Next to Owner on the top click Change (if prompted by the User Account Control dialog for permission click Yes).
    4. Type Administrator or Administrators into the field entitled Enter the object name to select, click Check Names to verify, then click OK repeatedly until all opened dialogs are closed.
  7. Clear all offline content and cookies from your web browser by following the instructions available on its vendor's website:

    Internet Explorer: Offline content/Cookies

    Mozilla Firefox: Offline content/Cookies

    Google Chrome: Offline content/Cookies

  8. Temporarily turn off any firewall software. If you are using Windows Firewall, follow the instructions on the Microsoft website:
  9. Download and install the latest version of Avast Antivirus. For detailed installation instructions, read the following article:
  10. Insert your license to Avast Antivirus. For detailed instructions about how to activate your subscription, read the following article:
  11. If you don't have Avast Premier or Avast Internet Security which include a built-in firewall, turn on your firewall software. For more instructions, refer to the relevant vendor documentation. If you are using Windows Firewall, follow the instructions on the Microsoft website:
  1. Uninstall Avast Antivirus from the system using the Avast Uninstall Utility as described in the following article:
  2. Manually delete any remaining Avast folders in the following default locations:

    64 bit type/version:
    • C:\Program Files (x86)\Avast Software or C:\Program Files (x86)\Alwil Software
    • C:\ProgramData\Avast Software or C:\ProgramData\Alwil Software


    32 bit type/version:
    • C:\Program Files\Avast Software or C:\Program Files\Alwil Software
    • C:\ProgramData\Avast Software or C:\ProgramData\Alwil Software
    Depending on your system preferences, the folders referenced above could be hidden. To display hidden files and folders in Windows 7, follow the instructions on the Microsoft website:
  3. Manually uninstall Avast Firewall Driver (or Avast Firewall NDIS Filter Driver) if it exists in the Properties of your Network connections, by following these steps:
    1. In File Explorer, right-click the Network icon on the left panel, and select Properties from the context menu to open Network and Sharing Center.
    2. Click Change adapter settings in the left panel to open Network connections.
    3. Right-click one of your connection icons (for example, Local Area Connection) and select Properties from the context menu.
  4. Reboot your computer and start Windows in Safe Mode by following the instructions on the Microsoft website:
  5. In Windows Safe Mode:

    Search and delete all files starting with aswNdis*.* if any exist in the following folder and its subfolders:

    • C:\Windows\System32\DriverStore

    Search and rename the file INFCACHE.1 to INFCACHE.1.BAK if it exists in the following default folders:

    • C:\Windows\System32\DriverStore
    • C:\Windows\Inf
  6. If Windows (started in Safe Mode) refuses to delete any of these files, take ownership of the files as follows:
    1. In File Explorer, right-click the file that you want to take ownership of, then click Properties from the context menu.
    2. Click the Security tab, and then click Advanced.
    3. Click the Owner tab, and then click Edit (click Yes if prompted by User Account Control dialog for permissions).
    4. Below the Name in the list click Administrator or click the Administrators group, then click OK repeatedly until all opened dialogs are closed.
  7. Clear all offline content and cookies from your web browser by following the instructions available on its vendor's website:

    Internet Explorer: Offline content/Cookies

    Mozilla Firefox: Offline content/Cookies

    Google Chrome: Offline content/Cookies

  8. Temporarily turn off any firewall software. If you are using Windows Firewall, follow the instructions on the Microsoft website: Turn Windows Firewall on or off
  9. Download and install the latest version of Avast Antivirus. For detailed installation instructions, read the following article:
  10. Insert your license to Avast Antivirus. For detailed activation instructions, read the following article:
  11. If you don't have Avast Premier or Avast Internet Security which include a built-in firewall, turn on your firewall software. For more instructions, refer to the relevant vendor documentation. If you are using Windows Firewall, follow the instructions on the Microsoft website:
  1. Uninstall Avast Antivirus from the system using the Avast Uninstall Utility as described in the following article:
  2. Manually delete any remaining Avast folders in the following default locations:

    64 bit type/version:
    • C:\Program Files (x86)\Avast Software or C:\Program Files (x86)\Alwil Software
    • C:\ProgramData\Avast Software or C:\ProgramData\Alwil Software


    32 bit type/version:
    • C:\Program Files\Avast Software or C:\Program Files\Alwil Software
    • C:\ProgramData\Avast Software or C:\ProgramData\Alwil Software
    Depending on your system preferences, the folders referenced above could be hidden. To display hidden files and folders in Windows Vista, follow the instructions on the Microsoft website:
  3. Manually uninstall Avast Firewall Driver (or Avast Firewall NDIS Filter Driver) if it exists in the Properties of your Network connections, by following these steps:
    1. In File Explorer, right-click the Network icon on the left pane, and select Properties from the context menu to open Network and Sharing Center.
    2. Click Manage network connections in the left panel to open Network connections.
    3. Right-click one of your connection icons (for example, Local Area Connection) and select Properties from the context menu.
  4. Reboot your computer and start Windows in Safe Mode by following the instructions on the Microsoft website:
  5. In Windows Safe Mode:

    Search and delete all files starting with aswNdis*.* if any exist in the following folder and its subfolders:

    • C:\Windows\System32\DriverStore

    Search and rename the file INFCACHE.1 to INFCACHE.1.BAK if it exists in the following default folders:

    • C:\Windows\System32\DriverStore
    • C:\Windows\Inf
  6. If Windows (started in Safe Mode) refuses to delete any of these files, take ownership of the files as follows:
    1. In File Explorer, right-click the file that you want to take ownership of, then click Properties from the context menu.
    2. Click the Security tab, then click Advanced.
    3. Click Owner. Below the Name in the list click Administrator or click the Administrators group, then click OK repeatedly until all opened dialogs are closed (click Continue if prompted by User Account Control dialog for permissions).
  7. Clear all offline content and cookies from your web browser by following the instructions available on its vendor's website:

    Internet Explorer: Off-line content/Cookies

    Mozilla Firefox: Offline content/Cookies

    Google Chrome: Offline content/Cookies

  8. Temporarily turn off any firewall software. If you are using Windows Firewall, follow the instructions on the Microsoft website:
  9. Download and install the latest version of Avast Antivirus. For detailed installation instructions, read the following article:
  10. Insert your license into Avast Antivirus. For detailed activation instructions, read the following article:
  11. If you don't have Avast Premier or Avast Internet Security which include a built-in firewall, turn on your firewall software.For more instructions, refer to the relevant vendor documentation. If you are using Windows Firewall, follow the instructions on Microsoft website:
  1. Uninstall Avast Antivirus from the system using the Avast Uninstall Utility as described in the following article:
  2. Manually delete any remaining Avast folders in the following default locations:

    32 bit type/version:
    • C:\Program Files\Avast Software or C:\Program Files\Alwil Software
    • C:\Documents and Settings\All Users\Application Data\Avast Software or C:\Documents and Settings\All Users\Application Data\Alwil Software
    Depending on your system preferences, the folders referenced above could be hidden. To display hidden files and folders in Windows XP, follow the instructions on the Microsoft website:
  3. Manually uninstall Avast Firewall Driver (or Avast Firewall NDIS Filter Driver) if it exists in the Properties of your Network connections, by following the steps below:
    1. In Windows Explorer, right-click the My Network Places icon in the left panel, and select Properties from the context menu to open Network connections.
    2. In Network connections right-click one of your connection icons (for example, Local Area Connection) and select Properties from the context menu.
  4. Reboot your computer and start Windows in Safe Mode by following the instructions on the Microsoft website:
    • Start your computer in safe mood
  5. Search and rename the file INFCACHE.1 to INFCACHE.1.BAK if it exists in the following default folders:
    • C:\Windows\System32\DriverStore
    • C:\Windows\Inf
  6. If Windows (started in Safe Mode) refuses to delete any of these files, take ownership of the files as follows:
    1. In Windows Explorer, right-click the file that you want to take ownership of, then click Properties from the context menu.
    2. Click the Security tab, and then click the Advanced button (if prompted by the Security message for permission click OK).
    3. Click Owner. Below the Name in the list, click Administrator or click the Administrators group, then click OK repeatedly until all opened dialogs are closed.
  7. Clear all offline content and cookies from your web browser by following the instructions available on its vendor's website:

    Internet Explorer: Offline content/Cookies

    Mozilla Firefox: Offline content/Cookies

    Google Chrome: Offline content/Cookies

  8. Temporarily turn off any firewall software. If you are using Windows Firewall, follow the instructions on the Microsoft website: Turn Windows Firewall on or off
  9. Download and install the latest version of Avast Antivirus. For detailed installation instructions, read the following article:
  10. Insert your license into Avast Antivirus. For detailed activation instructions, read the following article:
  11. If you don't have Avast Premier or Avast Internet Security which include a built-in firewall, turn on your firewall software. For more instructions, refer to the relevant vendor documentation. If you are using Windows Firewall, follow the instructions on Microsoft website:
  • Avast Premier 17.x
  • Avast Internet Security 17.x
  • Avast Pro Antivirus 17.x
  • Avast Free Antivirus 17.x
  • Microsoft Windows 10 Home / Pro / Enterprise / Education
  • Microsoft Windows 8.1 / Pro / Enterprise
  • Microsoft Windows 8 / Pro / Enterprise
  • Microsoft Windows 7 Home Basic / Home Premium / Professional / Enterprise / Ultimate
  • Microsoft Windows Vista Home Basic / Home Premium / Business / Enterprise / Ultimate
  • Microsoft Windows XP Home / Professional / Media Center Edition

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