How the list of Specially Designated Nationals and Blocked Persons is created?

"Specially Designated Nationals and Blocked persons" listed on a compliance policies are generally derived from governmental watchlists - each government will have its own criteria, though these overlap to an extent. It's important to keep in mind that these lists are constantly evolving with a country's particular requirements as well as global events.

Anti-Money Laundering and Know Your Customer systems and vendors will generally ensure that they check for such individuals in particular, and keep such lists up to date for their internal usage. Note that just because an individual is not specifically listed does not mean they are automatically clear with respect to Anti-Money Laundering.