MADISON, Wis. -- The University of Wisconsin-Madison is taking steps to better protect the identities of its staff members.

Starting on April 15, the university said that all ID cards that are based on Social Security numbers will no longer work.

UW-Madison is contacting some 8,000 staff members by e-mail to let them know about the mandatory badge turn-in.

The change comes after last November's leak in which personal information was accidentally posted on a Web site.

"We started with a voluntary program. We asked them to come in and get new IDs, and a lot of them did. But over time, and until we actually void the numbers, it's going to take yet a few more weeks to do away with the rest of them," said Brian Rust, communications manager at the UW-Madison Division of Information Technology.

The Union South ID office is waiving the $15 replacement fee for all faculty with IDs based on their Social Security number.

The change does not affect current students who are already randomly assigned ID numbers.