As much of a hassle as it is, you should consider working with your affected customers to close their accounts and reopen new ones. Also, a forensic study of affected accounts might find a common thread -- a check payee in common where account information might have been compromised. If you bring someone in to do this, get your customer's approval to review account records with the third party.
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John S. Burnett
BankersOnline.com
Fighting for Compliance since 1976
Bankers' Threads User #8