Officials with Frederick County Public Schools said about 1,000 former students were affected by a pre-2010 data breach that was discovered in September.
Schools spokesman Michael Raymond Doerrer said in an email Tuesday that students who attended county public schools between November 2005 and November 2006 were affected. He said the data includes names, Social Security number and date of birth.
The breach was brought to the school system's attention by a former student, who found his data on a website.
Doerrer said the school system notified the FBI as soon as it learned of the data breach and has been working with state law enforcement and technology officials.
Frederick County Public Schools will notify the former students who were affected.