Define Traffic to Decrypt

Use Decryption Policy rules to define the traffic you decrypt and the traffic you choose not to decrypt because of regulations, business reasons, or privacy reasons.
A Decryption policy rule allows you to define traffic that you want the firewall to decrypt and to define traffic that you choose to exclude from decryption because the traffic is personal or because of local regulations, for example.
Attach a Decryption profile to each Decryption policy rule to enable certificate checks, session mode checks, failure checks, and protocol and algorithm checks, depending on the profile. These checks prevent risky connections, such as sessions with untrusted certificate issuers, weak protocols, ciphers, and algorithms, and servers that have certificate issues.
Review the Decryption deployment best practices checklist to ensure that you understand the recommended best practices.
As a best practice, you should always block some URL Filtering categories such as malware, phishing, dynamic-dns, unknown, command-and-control, proxy-avoidance-and-anonymizers, questionable, and parked. Many companies also block the copyright-infringement and extremism URL categories. If you must allow any of these categories for business reasons, you must decrypt them and apply strict Security profiles to the traffic.
URL categories that you should always decrypt if you allow them include: online-storage-and-backup, web-based-email, web-hosting, personal-sites-and-blogs, and content-delivery-networks.
In Security policy, block Quick UDP Internet Connections (QUIC) protocol unless for business reasons, you want to allow encrypted browser traffic. Chrome and some other browsers establish sessions using QUIC instead of TLS/SSL, but QUIC uses proprietary encryption that the firewall can’t decrypt, so potentially dangerous traffic may enter the network as encrypted traffic. Blocking QUIC forces the browser to fall back to TLS/SSL and enables the firewall to decrypt the traffic.
Decrypting TLS traffic forces browsers that use HTTP/2 to fall back to HTTP 1.1 because the firewall can’t decrypt HTTP/2 traffic. Allow browsers to fall back to HTTP 1.1 so you can decrypt this traffic and prevent potentially dangerous traffic from entering the network as encrypted traffic.

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