Similar to the Location block, this chain logs and drops all traffic
from and to networks known to pose technical threats to IPFire users.
Doing so in a dedicated chain makes sense for transparency reasons, as
we won't interfer with other firewall rules or the Location block, so it
is always clear why a packet from or to such a network has been dropped.
Signed-off-by: Peter Müller <peter.mueller@ipfire.org>