A Deep Dive into Voice Fraud Migration and Revenue Recovery

In our previous post, Which Tools Are Most Critical to Identify, Monitor, and Stop International Voice Fraud?, we illustrated and discussed how important a holistic approach is to fighting fraud effectively. Today, we’re following up with new data and insights that further highlight the adaptive nature of fraud—and the need for a comprehensive, efficient, multi-layered defense strategy.

The Core Insight

International Voice Bypass Fraud constantly migrates to the least-cost and least defended Route. As a result, significant revenue recovery depends on a holistic approach. Professionals working in SIM Box detection will appreciate how visual evidence can validate what experience already teaches us: fraud is persistent and adaptive. Still, there’s great value (and pleasure) in clearly seeing the story unfold in the data.

Chart 1: Test Call Results OTT vs Sim Box

The red line represents test calls identified as OTT (Over-The-Top) Voice Bypass Fraud.
The blue line reflects calls linked to SIM Box Fraud.

Around March 25, Mobius rolled out OTT Voice Bypass blocking. OTT fraud dropped sharply—the red line nearly vanishes.
SIM Box fraud surged—the blue line spikes significantly.
Notably, brief jumps in OTT fraud on March 17 and March 25 align with brief interruptions in the blocking solution, highlighting fraud’s rapid response to gaps in protection.

Chart 2: Losses from On-Net SIM Box Fraud

This bar chart shows:

Blue segments: Losses before detecting a suspect SIM.
Orange segments: Losses after detection, until the network shuts the SIM down.

Key Observations:

Prior to March’s OTT blocking, few controls were in place.
Once OTT routes were blocked, fraudsters migrated to on-net SIMs, and resulting losses increased significantly.
It wasn’t until May 20 that the network implemented effective auto-shutdown mechanisms for these SIMs.

Chart 3: Losses from Off-Net SIM Box Fraud

This chart shows a similar structure, but for off-net SIMs.

As on-net SIM controls improved, fraudsters pivoted again—this time to off-net SIMs.
Blue segments: Losses before detecting a suspect SIM.
Orange segments: Losses after detection, until the network shuts the SIM down.
May 20 saw a dramatic rise in off-net SIM activity, coinciding with the network’s improved on-net shutdown capability.
After presenting these findings, the MNO implemented an off-net SIM auto shutdown feature as well.

Final Outcome

Initially, we were disappointed/panicked not to see an immediate spike in international voice revenue after blocking OTT Voice Bypass (e.g., WhatsApp/Viber). But the fraud didn’t disappear—it migrated.

Thanks to comprehensive test call data and DataSentry analytics, we were able to:

Track fraud as it migrated across Least Cost Routes (LCR)s.
Identify and recommend efficient countermeasures.
Help the MNO build layered defenses.

Result: We are now consistently delivering a sustained 10%+ daily increase in international voice minutes since the project began.