BRUSSELS, Dec 6 (Reuters) - Meta (META.O) cannot run advertising based on personal data and will need users' consent to do so, according to a confidential EU privacy watchdog decision, a person familiar with matter said on Tuesday.The Irish privacy regulator, which will issue the final decision, has been given a month by EU privacy watchdog the European Data Protection Board to do so.Its decision is likely to include hefty fines, the person said.Our Standards: The Thomson Reuters Trust Principles."