How to block facebook access

[John Levine]

In article <20170820153621.GA9420 at slackbox.erewhon.home> you write:
>I would hazard a guess that *most* facebook users wouldn't be technically
>savvy enough to use an IP-adres.

Even if they are, FB will redirect them to a name.  They'd either have
to use an external DNS cache or a VPN.  I suppose one could preemptively
block port 53 requests out to 8.8.8.8 and 8.8.4.4.

R's,
John