How to block Facebook and Gmail in CFS 3.0 - SonicOS 5.8 and above.
03/26/2020 
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DESCRIPTION:
This article describes the method to block Gmail.com and Facebook.com using CFS 3.0.
CFS examines the Server Extensions field in the Client Hello message and/or the CN in the Server Hello message to block HTTPS sites. HTTP sites are blocked by examining the Host field of the GET request. The following sections describe the methods involved in blocking both HTTP and HTTPS gmail.com and facebook.com.
RESOLUTION:
Enabling HTTPS Content Filter Globally
- Login to the SonicWall Management GUI
- Navigate to the Security Services | Content Filter page
- Click on Configure under Content Filter Type with SonicWall CFS selected.
- Check the box Enable HTTPS Content Filtering.
- Click on OK to save the settings.
Blocking using Forbidden Domains in CFS via Users and Zone Screens
- Select Via User and Zone Screens under CFS Policy Assignment.
- Click on Accept to save the change.
- Click on Configure under Content Filter Type with SonicWall CFS selected.(for 5.8.x.x)
Click on
Configure
under
Content Filter Type
with
Content Filter Service
selected.(for 5.9 and above)
- Click on the Custom List tab.
- Click on Add under Forbidden Domains and enter facebook.com and mail.google.com
- Click on OK to save the changes.
Configuring Custom CFS Policies to inherit the Allow/Forbidden Custom List.
What has been entered under the Forbidden Domains is automatically applicable to the Default policy. To enforce the same on custom CFS policies their Custom List Settings needs to be manually set to Global.
- Edit the custom CFS policy.
- Click on the Settings tab.
- Set the Source of Forbidden Domains to Global.
- Click on OK to save.
Blocking using Allow/Forbidden Custom List in CFS via App Rules
- On the Security Services | Content Filter page, select Via App Rules under CFS Policy Assignment.
- Click on Accept to save the change.
Match Objects
- Navigate to Firewall | Match Objects
- Click on Add New Match Object
To create a custom list of allowed or forbidden domains, select CFS Allow/Forbidden List under Match Object Type. You could also load the allow/block list from a file containing the name of the domains. Each entry in the file should be separated by a line. The maximum size of the file is 8192 bytes.
Unlike CFS via Users and Zones, Custom List Objects (as above) cannot be used individually in an App Rule. It can only be used with a CFS Category List Object (see below):
App Rules
- Navigate to the Firewall | App Rules page.
- Check the box under Enable App Rules.
- Click on Add New Policy and create the following App Rule.
Log Messages
When SonicWall CFS blocks HTTPS websites users will not see a blocked page only a connection-reset page.
However the following messages will appear in the logs:
Next Generation FirewallNext-generation firewall for SMB, Enterprise, and Government
Security ServicesComprehensive security for your network security solution
Capture Security applianceAdvanced Threat Protection for modern threat landscape
Network Security ManagerModern Security Management for today’s security landscape
Secure Mobile AccessRemote, best-in-class, secure access
Wireless Access PointsEasy to manage, fast and secure Wi-FI
SwitchesHigh-speed network switching for business connectivity
Cloud App SecurityVisibility and security for Cloud Apps
Cloud Firewall (NSv)Next-generation firewall capabilities in the cloud
Capture ClientStop advanced threats and rollback the damage caused by malware
Content Filtering ClientControl access to unwanted and unsecure web content
