If you use some kind of web filtering, this should be able to block it on your network. I just checked the PAN-DB-URL and that url is:
URL filtering can't be used because after "installing" the psiphon client, you need to initiate connexion.
These connexions are based on SSL then no URL filtering ... :-(
I do not know how the client works so I cannot see the traffic for myself. However you should still be able to see the URL's eventhough the traffic is SSL. Perhaps a submission for application detection is in order?
Submit an application:
Hope this helps...
Just in case you do use URL filtering:
Previous category: computer-and-internet-info
You suggested: proxy-avoidance-and-anonymizers
New category: proxy-avoidance-and-anonymizers
The new categorization is available starting with URL DB version: 2015.09.22.220
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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