Do not worry! The PlayStation Network has not been hacked again. It is just under going some important maintenance work. It does however mean the PSN will be out of action until 2.00 am Friday 18th November (GMT). You can still gain your trophies but playing online and shopping in the PlayStation Store is unavailable (unless you logged on before 16.00).
This is presumably another security measure by Sony to make sure the PSOutage of the summer does not happen again. Normal service should be resumed in the wee small hours of the morning.