Can my employer run a background check without me knowing?

An employer must obtain your permission in order to conduct a background check

Employers are permitted to run background checks.  However, there are many laws regulating the use of those background checks.  Part of the requirements is that you, as the employee, must consent to the background check before it is ran.  Typically, your consent is given through your signature on the notice. If you want to learn more about how employers may and may not use background checks click here