The Computer Fraud and Abuse Act (CFAA) is primarily focused on addressing unauthorized access to computer systems and protecting against computer-related fraud. Given this context, the behavior that would be protected under the CFAA is:
A person in another state accessing their bank account.
This activity involves accessing a computer system (the bank's system) that may be unauthorized if proper credentials are not used or if access is illegal.
The other options either do not relate to unauthorized access to computer systems (like downloading a song or posting comments) or may not violate CFAA protections (such as advertising online to children, which falls under different regulations).