mac_ifoff(4) interface silencing policy


To compile the interface silencing policy into your kernel, place the following lines in your kernel configuration file:
options MAC options MAC_IFOFF

Alternately, to load the interface silencing policy module at boot time, place the following line in your kernel configuration file:

options MAC

and in loader.conf5:



The interface silencing module allows administrators to enable and disable incoming and outgoing data flow on system network interfaces via the sysctl(8) interface.

To disable network traffic over the loopback (lo(4) ) interface, set the sysctl(8) OID security.mac.ifoff.lo_enabled to 0 (default 1).

To enable network traffic over other interfaces, set the sysctl(8) OID security.mac.ifoff.other_enabled to 1 (default 0).

To allow BPF traffic to be received, even while other traffic is disabled, set the sysctl(8) OID security.mac.ifoff.bpfrecv_enabled to 1 (default 0).

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The policy module first appeared in Fx 5.0 and was developed by the TrustedBSD Project.


This software was contributed to the Fx Project by Network Associates Labs, the Security Research Division of Network Associates Inc. under DARPA/SPAWAR contract N66001-01-C-8035 (``CBOSS'' ) as part of the DARPA CHATS research program.


See mac(9) concerning appropriateness for production use. The TrustedBSD MAC Framework is considered experimental in Fx .

While the MAC Framework design is intended to support the containment of the root user, not all attack channels are currently protected by entry point checks. As such, MAC Framework policies should not be relied on, in isolation, to protect against a malicious privileged user.