1. Notify credit bureaus

As soon as you've noticed the problem, your first action should be to call one of the three major credit bureaus — Experian, TransUnion, and Equifax. When you call one bureau, it will notify the other two, according to the Privacy Rights Clearinghouse. When you call, you will be able to place a 90-day, initial fraud alert on your report. If you prove that you were a victim of fraud, you will be able to extend the alert to seven years.