This page contains information regarding Star Trek: Picard, and thus may contain spoilers.
A security net was a type of force field.
The Dominion ketracel-white facility in the Alpha Quadrant was protected with a security net. When Captain Benjamin Sisko led a crew aboard a Jem'Hadar fighter to destroy the base in 2374, the security net was raised just as they prepared to leave, nearly taking them out with the facility. (DS9: "A Time to Stand")
A standard Romulan planetary defense system, such as the one installed on Vashti, consisted of orbital killer drones that generated an impenetrable security net. When La Sirena and Seven of Nine's ship battled Kar Kantar's Bird-of-Prey over Vashti in 2399, Kantar attempted to drive La Sirena into the security net. Seven's ship was destroyed when it was disabled and collided with the net. (PIC: "Absolute Candor")