Troubleshooting connection speed issues with Web Shield in Avast Antivirus

Web Shield is currently most sophisticated and important security component of the Avast Antivirus. The shield monitors network activities and as a result may slightly slow down the speed of internet activity. This difference is imperceptible in most cases, however some users do report noticeable reduction in web page load speeds. Tools offering "internet speed tests" can be inaccurate because they do not the evaluate the scanned connection correctly and confuse the Web Shield activity with the internet speed test server and local hardware.

Why is my high speed connection slower with Web Shield on?

High speed connections greater than 20Mbits/s may see noticeable slowdowns under certain conditions. For example, if a hard drive has an I/O speed of 30Mbits/s, the Web Shield scans slow down the page loading process because the hard drive I/O operations may be doubled during active scans. The internet input of 20Mbits/s Input plus 20Mbits/s of Web scanner data output can exceed the maximum hard drive throughput and lead to noticeable slowdown.

Are there specific devices that have compatibility issues with Web Shield?

Some network components or connection types may be incompatible with a parts of the Avast program or Web Shield in particular. The default setting for some routers and ADSL modems may expect a different connection or packet type. This mismatch can cause connection resets and timeouts. For example, the router sends a request to client network card and waits for a response but when the device evaluates the response as "uncommon" because it has a slightly different format. The device also may have a very short timeout setting and the delay caused by scanning causes the connection to timeout.

Avast monitors reports for specific devices and contacts device vendors when there is an issue we have a solution or workaround they can apply to their code. For a isolated incidents on specific devices we cannot propose any such solutions unfortunately. However, many issues are related to a specific setting of Web Shield and can be disabled while still providing adequate security protection.

Are there any workarounds to improve web performance when using Web Shield?

You can customize your Web Shield configuration or if absolutely necessary, disable some settings as workarounds for the web speed issue. These features can be disabled with only a minor impact on user security.

To adjust Web Shield settings, follow these steps:

  1. Open Avast Antivirus user interface and go to SettingsComponents
  2. Click Customize next to Web Shield.
  3. Change these settings:
    • Disable intelligent stream scanning: in the Main settings section, untick Use intelligent stream scanning. Unticking this box may speed up scanning and browsing. However, in some cases unticking the box can slow down web browsing even more.
    • Disable HTTPS scanning: in the Main settings section, untick Enable HTTPS scanning which protects your system against the malware delivered over HTTPS connections. If disabled, File Shield still scans all downloaded content before running any files.
    • Adjust Web Shield sensitivity: in the Sensitivity section, set Heuristic sensitivity to Off and untick Use code emulation. These options scan for standard versus potentially risky web behavior, but are not commonly used by Web Shield.

Outside of Web Shield settings, in SettingsComponents, you can also disable Real Site that helps to protect your internet activity from DNS hijacking. Even with this feature disabled, the File Shield protects you by scanning all content before allowing files and scripts to run. Furthermore, most internet providers monitor DNS requests as well.

  • Avast Ultimate 17.x
  • 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 - 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 1, 32 / 64-bit
  • Microsoft Windows Vista Home Basic / Home Premium / Business / Enterprise / Ultimate - Service Pack 2, 32 / 64-bit
  • Microsoft Windows XP Home / Professional / Media Center Edition - Service Pack 3, 32-bit

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