Viber Allowed and Working but no File Transer 80

Ktrippings Lv1Posted 2026-Jun-04 08:57

I have a client wanting to have viber and only selected internet sites allowed. Viber is working when sending and receiving messages, but file transfer does no work. Client does not want a blanket config, because when we allow certain protocols and applications in App control Policy, it also allows the many sites that should be denied . The problem we cannot isolate is the hidden protocol and destination that is being denied for file transfer. We tried to enable SSL for all destinations but it also allowed restricted sites to come through. is there any possible workaround to this to isolate allowing viber file transfer protocols?

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Prosi Lv3Posted 2026-Jun-04 11:14
  
Yes—it's a strict internet whitelist for applications like Viber.

The challenge is that Viber file transfers don't rely on the visible signature of the Viber application. But also on
- CDN/dynamic cloud destinations
- HTTPS over multiple domains
- SSL-encrypted traffic
- Sometimes QUIC/HTTP3
- Background API calls
For Sangfor NGAF, enable:
- SSL Decryption
- Threat intelligence logging
- Session tracking
- Application dependency visibility
Muhammad Abid Lv3Posted 2026-Jun-04 12:12
  
This is a common challenge because Viber file transfers often use different servers, CDN endpoints, and encrypted HTTPS connections than regular messaging. If messages work but file transfers fail, I would recommend:

Enable logging on the deny policy and attempt a file transfer.
Review NGAF traffic, application control, and URL logs during the test to identify the blocked application, domain, or destination IP.
Check whether SSL Inspection is enabled, as Viber file transfers may rely on encrypted HTTPS traffic that cannot be properly identified without decryption.
Create a specific allow rule for the detected Viber-related application, domain, or destination instead of allowing broad categories.
If CDN services are involved, monitor multiple transfer attempts because the destination may change dynamically.
Use packet capture on the NGAF during a failed transfer to identify the exact protocol and destination being blocked.

The best approach is usually to identify the blocked destination from logs or packet captures and create a targeted exception rather than enabling broad application or protocol permissions that may allow unwanted websites..

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