Call Filter — Reduce Blocking Solution

What is Call Filter and how does it reduce SIM blocking?

Call Filter is an advanced VoIP call filtering solution that reduces SIM blocking in GSM termination operations by intelligently filtering out suspicious calls, robot dialers, test calls, and Reduce fraud probes before they reach your SIM cards. It uses dual filtering technology — both callee number binding and caller ID binding — to ensure repeated calls go to the same SIM port, mimicking natural human calling patterns and extending SIM lifetime significantly.

How does the whitelist and blacklist system work in Call Filter?

Call Filter provides comprehensive whitelist and blacklist management. The whitelist allows you to define trusted numbers that are always permitted, while the blacklist blocks known suspicious numbers, test call sources, and Reduce fraud probes. You can add entries individually or bulk import via CSV files up to 2MB. The system supports regex patterns for advanced filtering, such as blocking all caller IDs starting with specific prefixes or matching exact digit lengths. You can also configure "allow only whitelist" mode for maximum protection.

What is callee number filtering and how does it extend SIM life?

Callee number filtering binds specific dialed phone numbers to specific SIM ports in your gateway. When a number like 0987654321 connects through port 1, all future calls to that same number are automatically routed through port 1. This creates consistent calling patterns that mobile operators expect from normal subscribers, reducing the suspicion that triggers SIM blocking. The system builds these bindings dynamically and maintains them with configurable lease times.

What is caller ID filtering and when should I use it?

Caller ID filtering binds calls from specific caller IDs (ANI/CLI) to specific SIM ports. When a call from caller ID "cloudfonica" connects through port 1, all future calls from that same caller ID route through port 1. This is particularly effective when your traffic comes from identifiable sources and you want to maintain consistent routing patterns. The choice between callee filtering and caller ID filtering depends on your operator blocking patterns — Call Filter supports both simultaneously for maximum protection.

How does the Performance Filter improve SIM protection?

The Performance Filter analyzes call statistics over configurable date ranges and automatically identifies numbers with poor performance metrics. You can set thresholds for minimum ACD (Average Call Duration), minimum ASR (Answer-Seizure Ratio), and minimum hits per hour. Numbers that fall below these thresholds are automatically blacklisted, preventing repeated low-quality calls that trigger operator Reduce fraud systems. This proactive filtering significantly reduces SIM blocking caused by bad traffic patterns.

Can Call Filter replace caller IDs to protect my identity?

Yes, Call Filter includes a Caller ID Replacement module that allows you to replace source caller IDs with numbers of your choice before sending calls through your gateway. This helps mask the origin of your traffic and prevents operator Reduce fraud systems from tracing patterns back to specific sources. You can configure replacement rules individually or bulk import replacement lists via CSV.

What is the Bucket system and how does it manage call distribution?

The Bucket system is Call Filter intelligent call distribution engine. Each bucket contains a list of callee numbers or caller IDs bound to a specific gateway port with configurable parameters: Bucket Size (maximum numbers per port), Lease Time (how long bindings remain active), and Call Gap (minimum time between calls to the same number). The system automatically builds and manages these buckets, ensuring even call distribution across all available SIMs while maintaining the binding consistency that prevents blocking.

How does Call Filter simulate human behavior to avoid detection?

Call Filter includes multiple human behavior simulation features: auto-increasing bucket sizes to gradually expand calling patterns, improvised call gap techniques to create natural pauses between calls, automatic outgoing call generation to simulate inbound call responses, monitoring of number/CLI length patterns, and intelligent distribution that prevents robotic calling patterns. These features work together to make your GSM termination operation appear indistinguishable from normal human mobile usage.

Is Call Filter compatible with my GSM gateway?

Call Filter is compatible with all major GSM gateway brands including GOIP (all models), Dinstar, Skyline, OpenVox, Antrax, Hybertone, Addpac, E-Join, ETS (Etross), 2N, Teles, and any SIP-compliant gateway. It also works seamlessly with softswitches like VOS3000, Asterisk, FreePBX, and any SIP-based routing platform. The system provides dedicated configuration guides for each supported gateway model.

What is the optimal SIM-to-call ratio for best results?

For optimal performance and minimal SIM blocking, the recommended ratio is 4 SIMs per concurrent call. Use 64 SIMs for 16 concurrent calls, or 128 SIMs for 32 concurrent calls. This provides sufficient rotation capacity for the Call Filter to distribute traffic naturally while maintaining binding consistency. Higher SIM-to-call ratios generally result in longer SIM lifetimes and better overall performance.

How do I configure incoming and outgoing prefixes for routing?

Call Filter provides comprehensive prefix management through the Manage Route section. Incoming Prefix configuration defines how calls enter the system and which filter type (callee or caller ID) applies. Outgoing Prefix (Bucket) configuration defines how filtered calls exit to specific gateways with bucket parameters. You can configure multiple prefixes, set callee/caller number mappings, perform bulk additions and removals, and manage carrier-specific routing rules. The system supports bulk CSV import for rapid prefix configuration.

Can I get a free trial of Call Filter?

Yes, VPN Worlds offers a free trial of Call Filter so you can evaluate its SIM protection capabilities with your existing infrastructure. During the trial, you can test whitelist/blacklist filtering, performance filtering, bucket management, and caller ID replacement features. Our technical support team is available 24/7 to assist with configuration and optimization during your evaluation period.