what is access_bpf group?
Wireshark's installer configures your system so that the user doing the installation can capture network traffic without the capturing program having to run as root.

The way it does this is to:


create an access_bpf group;
put the user into that group;
install a StartupItem (in older versions) or a launch daemon (in newer versions) that, when the system is booted, changes the permissions of the BPF devices to rw-rw--- and the group owner of the BPF devices to access_bpf;
arranges that the StartupItem/launch daemon run at that time.


Note, BTW, that this also allows you to capture traffic with Wireshark (or Wireshark's TShark or dumpcap programs) without having to run them as root, it also allows you to capture traffic with tcpdump without having to run it as root.