Troubleshooting when Avast Antivirus components no longer work properly

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 advanced technical knowledge, performing them is necessary to fully resolve the Avast Antivirus component issues and prevent them from happening in the future.

Instructions

Before proceeding with the troubleshooting steps below, ensure you are logged in to Windows as a user with administrator permissions, and all other programs in Windows are closed. For more information, refer to the following article:
  1. Uninstall Avast Antivirus 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, refer to the following Microsoft article:
  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 ExplorerWindows Explorer, right-click the Network icon in the left panel, and select Properties from the context menu to open the 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 steps in the article below:
  5. In Windows Safe Mode, search for and delete all files starting with aswNdis*.* if any exist in the following folder and its subfolders:
    • C:\Windows\System32\DriverStore
  6. In Windows Safe Mode:
    1. Search for and delete all files starting with aswNdis*.* if any exist in the following folder and its subfolders:
      • C:\Windows\System32\DriverStore
    2. Search for 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
  7. If Windows (started in Safe Mode) refuses to delete any of these files, take ownership of the files by following the steps below:
    1. In File ExplorerWindows Explorer, right-click the file that you want to take ownership of, then select Properties from the context menu.
    2. Select the Security tab, then click Advanced.
    3. Next to Owner on the top, click Change (if prompted for permission by the User Account Control dialog, 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.
    5. Below Name in the list, click Administrator or click the Administrators group, then click OK repeatedly until all opened dialogs are closed.
  8. Clear all offline content and cookies from your web browser. For instructions, refer to your web browser's support documentation.

    Microsoft Edge: Internet Explorer: Mozilla Firefox: Google Chrome:
  9. Temporarily turn off any firewall software. If you are using Microsoft Defender FirewallWindows Firewall, follow the instructions on the Microsoft website:
  10. Download and install the latest version of Avast Antivirus. For detailed installation instructions, refer to the following article:
  11. If you have a paid subscription, insert your activation code into your Avast Antivirus. For detailed instructions about how to activate your subscription, refer to the following article:
  12. If you don't have Avast Premium Security or Avast Omni, which include a built-in firewall, turn on your firewall software. For more instructions, refer to the relevant vendor documentation. If you are using Microsoft Defender FirewallWindows Firewall, follow the instructions on the Microsoft website:
  • Avast Omni 1.x
  • Avast Premium Security 20.x
  • Avast Free Antivirus 20.x
  • Microsoft Windows 10 Home / Pro / Enterprise / Education - 32 / 64-bit
  • Microsoft Windows 8.1 / Pro / Enterprise - 32 / 64-bit
  • Microsoft Windows 8 / Pro / Enterprise - 32 / 64-bit
  • Microsoft Windows 7 Home Basic / Home Premium / Professional / Enterprise / Ultimate - Service Pack 2, 32 / 64-bit

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