code: public ZAuth deny(String address)
      {
          Objects.requireNonNull(address, "Address has to be supplied for denial");
          return send(DENY, address);
      }
docs: Deny (blacklist) a single IP address. For all security mechanisms, this
  rejects the connection without any further authentication. Use either a
  whitelist, or a blacklist, not not both. If you define both a whitelist
  and a blacklist, only the whitelist takes effect.
  @param address