Blacklist

A blacklist is a database of blocked entities - customer names, email addresses, card numbers (hashed BINs), IP addresses, device fingerprints, or shipping addresses - that your payment system automatically declines due to previous fraud, chargebacks, or abuse. For high-risk merchants fighting elevated fraud rates, blacklisting prevents repeat offenders from making additional fraudulent purchases after their first successful fraud attempt is discovered.

Effective blacklisting operates at multiple levels: card-level blocking (block specific card BIN ranges associated with prepaid fraud cards), customer-level blocking (block email addresses, names, and phone numbers from previous fraudsters), IP/device blocking (block device fingerprints and IP addresses from fraud attempts), and shipping address blocking (block addresses receiving fraudulent orders). Sophisticated systems use fuzzy matching to catch variations - blocking "[email protected]" also blocks "[email protected]" and "[email protected]".

Shared blacklists multiply effectiveness by leveraging industry-wide fraud data. Instead of only blocking fraudsters after they defraud you, shared blacklists block known fraudsters before their first attempt against your business. Services like Ethoca/Verifi maintain shared fraud databases across thousands of merchants - a fraudster successfully defrauding Merchant A gets blacklisted across all participating merchants. For high-risk verticals with organized fraud rings, shared blacklisting prevents 60-75% of fraud attempts by blocking known bad actors preemptively.

Balance against false positives requires careful management. Overly aggressive blacklisting blocks legitimate customers: shared family IP addresses, corporate networks, hotels, and VPNs generate false blocks. The optimal blacklisting strategy combines permanent blocks (confirmed fraudsters, chargebacks for fraud), temporary blocks (suspected fraud pending investigation), risk scoring increases (flagged entities require additional verification), and whitelist overrides (manually approved customers bypass blacklist checks). MIDs' fraud platform provides tiered blacklisting with automatic decay - low-confidence blocks expire after 90 days while confirmed fraud blocks remain permanent.