Support: Avast WebShield and Connection Speed


Avast Web shield is currently most sophisticated and important component of the Avast protection suite. 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.

The following are the most common reasons web browsing can be slowed down:

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.

Fortunately many issues are related to a specific component 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, turn off the scan as workarounds for web speed issue. These features can be disabled with only a minor impact on user security.

  • Disable Intelligent Stream scanning In the choose Settings, Active Protection menu click Customize next to Web Shield. Unchecking this box may speed up scanning and may speed up browsing. However in some cases unchecking the box can slow down web browsing even more.
  • Customize WebShield sensitivity Uncheck the Heuristic option and Emulation code options These features scan for standard versus potentially risky web behavior, but are not commonly used by Web Shield.
  • Disable HTTPS scanning You can uncheck the Enable HTTPS scanning in the Customize setting of Web Shield. HTTPS scanning protects your system against the malware delivered over HTTPS connections. If disabled, remember that the Avast File Shield still scans all downloaded content before running any files.
  • Disable Secure DNS Secure DNS scanning helps to protect your internet activity from snooping. 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 and can detect problematic DNS request and refuse connections to them automatically.
  • Avast Premier 2015
  • Avast Internet Security 2015
  • Avast Pro Antivirus 2015
  • Avast Free Antivirus 2015
  • Avast for Business 2015
  • Avast Mac Security 2015
  • Microsoft Windows 8.1 / Pro / Enterprise
  • Microsoft Windows 8 / Pro / Enterprise
  • Microsoft Windows 7 Home Basic / Home Premium / Professional / Enterprise / Ultimate
  • Apple Mac OS X 10.9.x (Mavericks, Intel-based)
  • Apple Mac OS X 10.8.x (Mountain Lion, Intel-based)
  • Apple Mac OS X 10.7.x (Lion, Intel-based)
  • Apple Mac OS X 10.6.8 (Snow Leopard, Intel-based)

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