Final answer:
The SDN lists subject to U.S. sanctions are maintained by the Office of Foreign Assets Control and identify sanctioned parties to help businesses avoid transactions with them.
Step-by-step explanation:
The main subject of the SDN lists is to identify individuals, groups, and entities, such as terrorists and narcotics traffickers, that are subject to U.S. sanctions.
These sanctions are designed to restrict the targets' access to the U.S. financial system and to prohibit U.S. persons from conducting business with them. The SDN list — Specially Designated Nationals and Blocked Persons List — is maintained by the Office of Foreign Assets Control (OFAC), which is an agency of the U.S. Department of the Treasury.
The list is easily accessible on the Treasury's website and is frequently updated as international relations and U.S. foreign policy goals evolve. It serves as a compliance tool for U.S. and international businesses to ensure they are not engaging in transactions with sanctioned parties.