In my experience SSL decryption and blocking the application Psiphon was not enough, it was only the first step. Psihon was stll able to connect. I discovered that Psiphon creates a Proxy service on localhost and changes proxy settings in browser to redirect browser traffic over Psiphon application. Psiphon application then forwards the traffic to the internet by its own sneaky methods:) I did Wireshark analysis and discovered that after SSL connection was blocked by PAN, Psiphon created a gzip encoded streaming tunel over tcp port 80 and PAN recognised it as "web-browsing" which was allowed. I tried to create a custom application but without success.
We successfully blocked the Psiphon by implementing SSL Decryption, blocking Psiphon application in the security policy and also by preventing users from changing their proxy settings using domain group policy.
Creating custom application signature for port 80 traffic and blocking it in the security policy on PAN would be more elegant but my signature caused too many false positives and it was easier to create a group policy.
from my testing, blocking just Psiphon while using decryption was not enough. If you leave the client to try and connect long enough, it will still connect.
The best results I've got was by blocking the following:
ipsec (not ipsec-udp)
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