example of checking if domains are blocked using CleanBrowsing.org, which returns an NXDOMAIN with a special authority section upon block

dns-block-check-example.bash

#!/usr/bin/env bash
# Quick script to test if names are blocked using CleanBrowsing.org's Family
# Filter DNS servers
DNS_SERVER='185.228.168.168'
BLOCKED_AUTH="cleanbrowsing.rpz.noc.org."

domain_is_blocked() {
  for name in "$@"; do
    result=$(dig "$name" @${DNS_SERVER})
    if echo "$result" | grep -q 'status: NXDOMAIN'; then
      if echo "$result" | grep -A1 ';; AUTHORITY' | awk '{ print $5 }' |
        grep "$BLOCKED_AUTH"; then
        echo "Blocked: $name"
      else
        echo "Real NXDOMAINi: $name"
        return 1
      fi
    else
      echo "Not blocked: $name"
      return 2
    fi
  done
}

# Functional tests
test_domain_is_blocked() {
  if [ $# -ne 2 ]; then
    echo "Expecting two arguments for test" >&2
    return 2
  fi
  if
    domain_is_blocked "$1" >/dev/null
    [[ $? == "$2" ]]
  then
    echo 0
  else
    echo 1
    return 1
  fi
}

# Run some test cases
test_domain_is_blocked "reddit.com" "0"
test_domain_is_blocked "google.com" "2"
test_domain_is_blocked "sdfafdadsfjk.example.com" "1"