Why Most Circular‑Chain Alerts Miss the Mark: My 9‑Step Forensic Playbook for Nagad Wallets
AI-generated illustration High‑Stakes Hook It was 02:17 am on a rainy Thursday in Dhaka. My phone buzzed with an urgent BFIU notice: BDT 27 million moving through seven Nagad wallets in a perfect loop, each hop under the BDT 100,000 MFS velocity threshold . The audit team was breathing down my neck. If we didn’t surface the chain before the regulator’s next checkpoint, we would be on the front page of the daily financial news. I stared at the raw CSV export – rows of sender_id, receiver_id, amount, timestamp . Nothing screamed “suspicious”. No single transaction breached the 100k rule. No classic structuring pattern. Yet the regulator’s red flag was real. The Hidden Problem Most of us build circular‑chain detectors that start with a simple velocity check or a single‑node repeat . In Bangladesh that works for obvious structuring, but it collapses when criminals spread the amount across many tiny hops. The BFIU guidelines (Section 3.2.4) explicitly warn: “ circular transfers below the...