This read-only counter tracks the total number of frames the bridge has filtered -- that is, deliberately not forwarded -- since it was last reset. An admin watches this counter to confirm that configured filtering rules (from the acquired, permanent, or special databases) are actively taking effect on real traffic. For example, after adding a filter to block traffic from a misbehaving device's address, a rising bdgdeviceFrFlt count confirms the bridge is indeed intercepting those frames rather than forwarding them.