This is a bit of a head scratcher with 6.0.x. Below are the 2 variables defined for address-groups:
HOME_NET: "[10.0.0.0/8,172.16.0.0/12,192.168.0.0/16,220.127.116.11/4,169.254.0.0/16]" EXTERNAL_NET: "[!$HOME_NET, 10.10.10.10/32]"
I have created a silly rule as:
alert tcp any any -> $EXTERNAL_NET any (msg:"My silly signature"; classtype:misc-activity; sid:3450000; rev:1;)
The goal is just to make sure things trigger the right way.
While the very same set of address-groups works fine in 4.x, I cannot figure out why EXTERNAL_NET definition does not trigger, but if I restrict it to:
then everything works as expected.
( I have tried different orders, different bracketting, … nothing helped).
Does this look like “user error”? did I skip a chapter in the book? any other idea?