What aspect of security does a firewall primarily address?

A firewall primarily addresses the aspect of security related to protecting a private network from unauthorized access. This is accomplished by monitoring and controlling incoming and outgoing network traffic based on predetermined security rules. Firewalls serve as a barrier between a trusted internal network and untrusted external networks, such as the Internet, ensuring that only legitimate traffic is allowed to enter or exit the network.

In a digital context, firewalls can be hardware devices or software applications designed to filter packets of information, blocking or allowing data transmission based on specific security policies. This function is vital in preventing unauthorized access, data breaches, and cyber attacks, thus maintaining the integrity and confidentiality of the network.

Considering the other options, physical security concerns the actual safety of bank properties (not the network); insurance against financial losses pertains to financial risk management rather than cybersecurity measures; and employee cybersecurity training focuses on educating personnel about safe practices in handling digital information rather than the technical aspect of network security provided by firewalls.