Proper Protocol for Web "Console" App?

In applications such as a Paypal listener app, where the app’s sole purpose is to respond to URL requests and not to display a page, I am confused about how to handle all those pings and hits that are not intended or legitimate. Wonder what common practice is for those.

Since the app processes code in the HandleURL event, for a legitimate hit I respond with

request.status = 200; return true

For everything else - if I want to treat them all the same what is the traditional way of handling? Is it

request.status = 404; return true ?

I am probably less concerned about the status code - I can choose the one that matches most closely to what I want to convey, but I am not clear on whether or not I should return true or if I should return false.

Return true indicates I have seen the hit, consciously dismissed it, and have no need for any further action - which I think is correct; do you agree?

If you don’t return true, a generic 404 error page is sent back. True means “I’ve handled this” to the framework.