How can I block specific websites using the Truffle?

Domain blocking can be accomplished by creating a rule in the ‘Domain Name Blocking / DNS Redirection’ section on the Advanced page. There you will enter the domain name that you wish to block (and leave the IP field blank). An example is shown in the screenshot below.

The site is blocked by redirecting DNS for the specified domain so any device using the Truffle for DNS (which includes any devices getting DHCP from the Truffle) will be blocked from accessing the specified site.