Voice Traffic Filter Overview
Voice Traffic Filter (VTF) is a configurable call filtering and network security application for your voice channel. When VTF is implemented, calls to the enterprise can be filtered through a series of analytic steps including a dynamic database of known spam, scam, and robocall numbers, STIR/SHAKEN scoring data, as well as an organization-specific set of rules applied to incoming calls.
Any flagged call can be immediately dropped or redirected by enterprise policy without ringing through, reducing disruption and protecting users and the voice network from potential criminal intrusions.
Now that you’ve successfully logged in, you’ll be guided through a short tour (15–20 minutes) to help you understand features, manage voice traffic, and see how callers experience your filter criteria.
Configuration Page
From the top of the page, you can toggle between:
- FILTER CALLS – Takes action on calls after analysis
- MONITOR ONLY – Allows all calls, but still analyzes activity
If MONITOR ONLY is selected, all calls are allowed regardless of results.
Each of the four layers of protection can be enabled or disabled:
- Enabled → shown with a green indicator
- Disabled → shown with a grey indicator
Aangepaste regels
Custom Rules can be enabled to define how specific callers or callees are handled.
It is recommended to leave this feature enabled.
GEROERD/GESCHUD
Configure how VTF handles STIR/SHAKEN validation data in your system.
- Delivered via SIP signaling
- Uses the “verstat” parameter for validation results
- Actions can be assigned based on validation outcomes
- Actions can also be set for calls without a “verstat” parameter
Proprietary Dynamic Database (PDD)
The PDD is a continuously updated defense against spam, scam, and vishing attacks.
- Uses global threat intelligence sources
- Tracks and verifies millions of numbers
- Checks incoming calls against multiple databases
- Applies configurable actions when numbers are flagged
Tips:
- Start with a “do-no-harm” approach using CAPTCHA actions
- Enable PDD early to benefit from continuous updates
CAPTCHA
Voice CAPTCHA helps differentiate bots from human callers and reduces the risk of blocking legitimate traffic.
Recommended settings:
- Digits: 2–3
- Seconds: 10
- Attempts: 2–3
Tip:
Send TN-Validation-Failed calls to CAPTCHA and drop failures, as these are often unreliable callers.
Exercise 1 – Getting Familiar with VTF
From the Call Activity page:
- Call one of your phone numbers
- Refresh the page to see the call at the top
- Review the action taken on the call
Head to the Custom Rules page:
- Create a rule:
- From = your phone number
- To = called number
- Action = Drop
Back to Call Activity:
- Call again → the call should drop
- In Monitor Mode, it will show what would have happened
- Refresh to confirm rule behavior
Exercise 2 – CAPTCHA Testing
Edit the rule:
- Change Action to CAPTCHA-Drop
- Save
Test calls:
- Call and enter digits correctly → observe result
- Call and enter digits incorrectly → observe dropped call
- Refresh to review results
Delete the rule:
- Return to Custom Rules
- Delete the rule
- Call again → confirm the call is allowed
Ongoing Use
- Review call activity regularly
- Check trends weekly during the first month
- Use Custom Rules to block, route, or allow callers
- Monitor how each call is handled in Call Activity
Ondersteuning
For platform issues, contact support and include:
- Tenant name
- Tenant ID
- Timeframe
- Example calls
