A Layer 7 firewall rule is a type of firewall rule that operates on the seventh layer of the Open Systems Interconnection (OSI) model, also known as the application layer.Unlike Layer 3 firewalls that filter traffic based on IP addresses, Layer 7 firewalls can analyze the contents of data packets to see if they contain malware or other cyber threats.Layer 7 firewalls categorize all traffic into "applications" and then allow you to block/allow traffic based on the application.