Using Sophos Anti-Virus® results in slow browsing experience

Article #: Product Castle


Users on workstations that are running Sophos Anti-Virus and Link Checker are reporting very slow internet access.


The Sophos Anti-Virus application, with the web anti malware checker enabled, accesses its web database before it allows users to access web sites.

Note that NTLM authentication for Guardian is not supported by the Sophos applications; they are unable to contact their server and so connections to the requested site are slow. The user may also receive an authentication pop-up that appears to be unrelated to the site the are accessing.


  1. Add the following domains to a custom category:
  2. Add the newly create custom category to Guardian's authentication exception list.
  3. Create a whitelist policy for the newly created category.


Last updated: Author: Contributions by:
30 August 2016   Tanja