OFAC maintains the Specially Designated Nationals list and a set of country and sectoral sanctions programs. US persons, and often anyone touching US dollars or US-origin services, must not deal with listed parties. Financial firms run automated sanctions-screening at onboarding and continuously afterwards.
Liability is strict: a violation can be penalised even without intent, which is why matches are handled conservatively and accounts are frozen first and investigated later. Blocked property must be reported and cannot simply be returned.
For traders the practical consequence is friction. A name resembling a listed party, a payment routed through a sanctioned jurisdiction, or a crypto address with tainted history can freeze an account until compliance clears it.
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