I block all outbound traffic on several of my CentOS 7 boxes and have logging rules just before the reject rules.  I get zero hits.<p>This includes 2 workstations.  In fairness, my &#x2F;etc&#x2F;resolv.conf points to recursive cache servers on my vpn, but I do log all my DNS queries.  The only log entries are for things I ask for and Firefox trying to dial home.