Poolstars 8 ball Rules say:
The Break
The break in one game matches is determined randomly. In multi-game matches the break will alternate.
1. The player breaking has ball-in-hand anywhere behind the headstring.
2. At least four object balls must touch a rail in order for the break to be legal.
3. If the shooter fails to drive enough object balls to the rail on the break, the opponent has the option of accepting the position or re-racking the balls and breaking himself.
But:
the game does not recognise less than 4 balls hitting the rail as a foul 
