code: public static void setTheManager() {
      if ("true".equalsIgnoreCase(System.getProperty(ACTIVATE_FLAG))) {
        if (!(System.getSecurityManager() instanceof DnsMonitorSecurityManager)) {
          System.setSecurityManager(theManager);
        }
      }
    }
docs: Update's the system's security manager to an instance of this class if
  system property dns_call_stack_logging is set to true.