This page contains information regarding Star Trek: Picard, and thus may contain spoilers.
The Fenris Rangers were an organization active in the late 24th century, based on Fenris. They were considered vigilantes. They operated Corsairs, and kept their money on Freecloud. (PIC: "Stardust City Rag")
Prior to the Qiris sector's descent into chaos, which created a power vacuum that attracted smugglers and petty warlords, this sector was within the territory of the Fenris Rangers, who helped the settlers of the planet Vashti with the installation of their planetary defense system. However, their resources were limited, and the organization became too ill-equipped to handle the crisis in the sector, prompting the Fenris Rangers to withdraw. (PIC: "Absolute Candor")
Seven of Nine and Icheb, the latter on leave from Starfleet, both joined the organization. Seven was still operating as a Ranger in the Qiris sector when Jean-Luc Picard and his associates encountered her in 2399. (PIC: "Stardust City Rag")