In an HA (High Availability) pair running in Active/Passive mode, the dataplanes communicate over the HA3 interface. This interface is used for the synchronization of session information and other runtime data between the active and passive firewalls, ensuring stateful failover and seamless transition in case of a failure.

https://docs.paloaltonetworks.com/pan-os/10-1/pan-os-admin/threat-prevention/dns- security/enable-dns-security

WildFire, a cloud-based threat analysis service from Palo Alto Networks, is capable of detecting zero-day malware across several types of traffic, including SMTP, HTTPS, and FTP. By analyzing files transmitted over these protocols, WildFire can identify malicious activities that traditional security measures might miss.
SMTP (Simple Mail Transfer Protocol) is used for email transmission, HTTPS (HyperText Transfer Protocol Secure) secures web traffic, and FTP (File Transfer Protocol) is used for file transfers. These protocols are commonly exploited by attackers to distribute malware, making WildFire's ability to monitor and analyze them critical for comprehensive network security.