I don't know specifically about RainLoop, but I usually put services like that behind a BasicAuth on the web server. It's a simple but effective way to protect

I don't know specifically about RainLoop, but I usually put services like that behind a BasicAuth on the web server. It's a simple but effective way to protect myself from PHP/application vulnerabilities - at a minor annoyance to the users (authenticating twice, every once in a while).