D.R. Horton (DHI) is telling customers of its DHI Mortgage subsidiary that their personal data may have been compromised following an attack on their software.

Unknown external sources breached DHI's Internet Loan Prequalification System.

DHI Mortgage, "took immediate steps to remedy the breach by isolating the affected server, purging certain affected files and modifying our electronic security measures to address the specific issue," the company said.

DHI is emailing instructions to customers who may be affected.

Founded in 1978 in Fort Worth, Texas, D.R. Horton operates in 73 markets in 25 states in the East, Midwest, Southeast, South Central, Southwest and West regions of the United States. D.R. Horton also provides mortgage financing and title services for homebuyers through its mortgage and title subsidiaries.