MIDDLEBURY - Supermarket grocery chain Hannaford Brothers, with outlets in Vermont, announced that a security data breach has affected its 4.2 million credit- and debit-card using customers; since December, 1,800 fraud cases have been reported. Company officials admitted that they knew about the mess for two weeks before they went public with the news March 17. The breach actually began on Dec. 7, 2007, and continued until at least the end of last week. Anyone who used a credit or debit card during the period at the chain s 165 outlets (and 106 Sweetbay stores in Florida) faces potential credit-abuse problems. Hannaford officials said the breach does not involve the names, addresses and telephone numbers of customers, but that was little consolation to shoppers. "Wow, this is very disturbing," said Michelle Rebon, age 42, a regular shopper at the Middlebury Hannaford. "I like shopping here, but I'd be concerned about their ability to keep my personal data secure." The U.S. Secret Service is involved with the investigation into the breach.