Section 31 is one of Star Trek's most mysterious organizations, and there are only a handful of known members of the covert Starfleet Intelligence agency. First introduced in Star Trek: Deep Space Nine, the intelligence organization caught the attention of Dr. Julian Bashir (Alexander Siddig) and Captain Benjamin Sisko (Avery Brooks) during the Dominion War. Section 31 were effectively given carte blanche to use whatever means necessary to protect the Federation, resorting to attempted genocide and intervening in Romulan politics. Section 31 saw themselves above the Prime Directive, and would stop at nothing to achieve their goals.

https://screenrant.com/every-known-member-of-star-treks-section-31/