17 CFR § 160.12 - Limits on sharing account number information for marketing purposes.
(a) General prohibition on disclosure of account numbers. You must not, directly or through an affiliate, disclose, other than to a consumer reporting agency, an account number or similar form of access number or access code for a consumer's credit card account, deposit account or transaction account to any nonaffiliated third party for use in telemarketing, direct mail marketing or other marketing through electronic mail to the consumer.
(1) To your agent or service provider solely in order to perform marketing for your own services or products, as long as the agent or service provider is not authorized to directly initiate charges to the account; or
(2) To a participant in a private-label credit card program or an affinity or similar program where the participants in the program are identified to the customer when the customer enters into the program.
(c) Example. An account number, or similar form of access number or access code, does not include a number or code in an encrypted form, as long as you do not provide the recipient with a means to decode the number or code.