When unauthorized access to the network has occurred as a result of bypassing underlying security mechanisms. This could be someone coming through the firewall or entering the network via a phishing email. At this point a data breach has not occurred.

A data breach happens after a network breach, when an individual or an application illegitimately enters a private, confidential or unauthorized logical IT perimeter and steals confidential or unauthorized data such as private consumer information, credit cards, IP etc.