South Carolina says a massive security breach exposed millions of Social Security numbers as well thousands of valid credit card numbers of state residents. The state Department of Revenue acknowledged the massive electronic security breach Friday, reporting a computer intrusion that led to 3.6 million Social Security numbers being stolen in a state with a population of approximately 4.7 million. The department learned of the intrusion on October 10, although it has not said how, and alerted federal and state law enforcement, CNET reported. USA Today suggested the hacker may have contacted the state demanding a ransom \"We are taking immediate steps to protect the taxpayers of South Carolina, including providing one year of credit monitoring and identity protection to those affected,\" Gov. Nikki Haley said in a statement. Anyone who has filed a South Carolina tax return since 1998 is being urged to call (866) 578-5422 to enroll in a consumer protection service and visit protectmyid.com/scdor, CNET reported.