The South Carolina Department of Revenue had a large and unprecedented security breach that went on for ten days before it was stopped. 3.6 million social security numbers and 387,000 credit card numbers were exposed by the hackers, though only 16,000 of the credit card numbers were unencrypted.
Anyone who has filed a tax return in SC since 1998 should call the number provided by the SC DOR. They will be able to find out if they were compromised and, if they were, get free credit monitoring from Experian. The phone number was overwhelmed initially, but the SC DOR said it plans on increasing the number of lines and operators.
Here is a quote from the press release with the phone number:
who has filed a South Carolina tax return since 1998 is urged to visit
protectmyid.com/scdor or call 1- 866-578-5422 to determine if their
information is affected. If so, the taxpayer can immediately enroll in
one year of identity protection service provided by Experian.
Here is a link to the full release: http://www.sctax.org/News+Releases/20121009_1026NR.htm