Credit report giant Equifax says some 143 million mostly US customers have had their information compromised in a cyber security breach.The company has said that credit card numbers for approximately 209,000 U.S. consumers were accessed, along with some dispute documents that contained personal identifying information for approximately 182,000 U.S. consumers.Equifax is offering a number of services for free to people, including credit monitoring. (You can find more information here, and see our expert advice below on protecting your data.) The breach happened mid-May through July and was discovered July 29, Equifax said. It also said it has seen no evidence of unauthorized activity on its core consumer or commerical reporting databases. "It's one of the worst hacks imaginable," said Dan Guido, CEO of the cyber-security firm Trail of Bits. "People should be extraordinarily angry at companies like Equifax. We place a huge amount of trust in them about money matters but they're so easily compromised by simplistic attacks like this one."Indeed, Guido wonders whether this major breach might mark the beginning of a "post-authentication era," in which this widely accepted personal information becomes essentially useless in establishing an individual's identity.