$ GET https://www.pingdom.com/rss/probe_servers.xml | \
awk --field-separator "[><]" '/:ip/ {print $3;}' | \
sort --numeric-sort --field-separator=. --key=1,1 --key=2,2 --key=3,3 --key=4,4 | \
sed "s/^/ALL: /" | \
sudo tee --append /etc/hosts.deny