Enabling the Short Duration filter tells the system to record behavior and build profiles so that it can block ANIs that it understands to have a known history of above 20% short duration calls. Refer to the Filter Report under Reporting in the UI to see how much Short Duration is being blocked via learned behavior.
Please note that there are some caveats to this as the system will need:
- Steady traffic
- "Normal" behavior
- At least 100 attempts in order to start building the profile
- There is the possibility that ANIs could be rotated so by the time a profile is built, the ANI is not used anymore