You can freeze your credit—preventing anyone from opening a new credit account in your name until the freeze is lifted—via the major reporting bureaus. (The three main agencies used in the U.S. are Equifax, Experian and TransUnion.) Such an incident offers a sobering reminder to practice good password hygiene going forward. Don’t reuse passwords—their complexity and uniqueness are powerful—and consider a manager such as 1Password. Americans can check whether their SSN was exposed via a tool such as Pentester’s NPD Breach Check. At the website Have I Been Pwned?, launched by Australia-based online security consultant Troy Hunt in 2013, visitors can see whether their e-mail addresses have been exposed in data breaches; an offshoot project similarly evaluates passwords.