find if 0-day flash bug was exploited (on a particular machine)

There have been several critical 0-day exploits in the past days/weeks in Flash alone. Nobody knows how long the 0-days have been exploited, and it is reasonable to expect that there are 0-days being exploited at this moment, but we don't know.

The practice of patching/updating flash plugin after 0-day has been discovered seems inadequate to me.

How could one check, if particular machine has been exploited? The 0-day in flash allows arbitrary code execution. AFAICT, The executed code could be anything

Is there any way to find out, that an exploit was used and that some code was executed?