OFAC maintains the List of Specially Designated Nationals and Blocked Persons (SDN List) as well as other sanctions lists, including: Sectoral Sanctions Identification List, Foreign Sanctions Evaders List, Non-SDN Palestinian Legislative Council List, Non-SDN Iranian Sanctions List, List of Foreign Financial Institutions Subject to Part 561, List of Persons Identified as Blocked Solely Pursuant to Executive Order 13599, and the List of Foreign Financial Institutions Subject to Correspondent Account of Payable-Through Account Sanctions.  OFAC’s consolidated sanctions list is available here.

US persons are generally prohibited from engaging in any transaction in which an SDN has an interest or an entity in which an SDN holds a 50% or greater share (directly or indirectly) has an interest.  All assets of the designated individuals and entities that are subject to US jurisdiction, and of any subsidiary owned 50% or more, must also be blocked.  See OFAC Guidance on entities owned by persons whose property and interest in property are blocked (50% Rule) here.