code: function(host, whitelist, next) {
      var blacklist = this.options.blacklist;
      helper.resolveHost(host, function(err, aRecords, resolvedHost) {
        var inBlacklist = false;
        if (!err) {
          if (whitelist) {
            if (_.intersection(aRecords, whitelist).length ) {
              next(err, [], aRecords);
              return;
            } else {
              for (var i = 0; i < whitelist.length; i++) {
                if (resolvedHost === whitelist[i]) {
                  next(err, [], aRecords);
                  return;
                }
              }
            }
          }
  
          inBlacklist = _.intersection(aRecords, blacklist)
        }
        next(err, inBlacklist, aRecords);
      });
    }
docs: tests whether host is in blacklist