Oracle has been investigating a point-of-sale system breach that may be the work of Russian cyberthieves. Hackers compromised at least 700 computers on the MICROS POS system, used by hundreds of thousands of hotels, restaurants and retail outlets worldwide to process credit card transactions, Krebs on Security reported earlier this month. More than 330,000 cash registers worldwide use MICROS, which ranks as one the world's three largest POS systems. Oracle confirmed that it has alerted its customers about the intrusion.