How to block facebook website
Remember, you need to configure DNS on the ScreenOS device before the address book items can resolve the DNS to an IP address.
In this example, we assume the hostname is SSG5, the domain name is abc.com, the primary DNS is 1.1.1.1, and the secondary DNS is 1.1.1.2
Click Network > DNS
Host Name: SSG5
Domain Name: abc.com
Primary DNS Server: 1.1.1.1
Secondary DNS Server: 1.1.1.2
Click Apply
Click Objects > Addresses > List
Select Untrust
Click New
Address Name: www.facebook.com
Click domain name, and enter www.facebook.com
Zone: Untrust
Click OK
Click Objects > Addresses > Group
Zone: Untrust
Click New
Group Name: Facebook
Move www.facebook.com from Available Members to Group Members by clicking the << button
Click OK
Click Policies
Select From Trust to Untrust, then click New
Source Address: Click Address Book, and select ANY
Destination Address: Click Address Book, and select facebook
Service: ANY
Action: DENY
Click OK
hope this helps you