It all depends on how you are running ZAP, and how you have configured it :)
By default ZAP only does what you tell it to do, so it you are running the ZAP desktop it will only run the Active Scanner when you tell it to, and you can tell it what to attack.
Have a look at that link and if you have any more questions about this then let us know how you are running ZAP.
Cheers,
Simon