Files with the extension .BFR are 'capture' files associated with 'NI Observer' (Network Instruments Observer).

The Network Instruments Observer is a network monitor and protocol analyser for Ethernet, Fibre Channel, Wireless 802.11 a/b/g, WAN (E1/E3), Token Ring and FDDI, providing metrics, capture and trending for both shared and switched environments.

.BFR capture files contain details of LAN traffic, etc.