[cesarb]

Well, it's hard for a Linux server distribution to not come with a firewall installed, since it's part of the kernel; all Linux distributions I've seen (including tiny floppy-disk-based Linux distributions) come with the firewall module enabled in the kernel configuration.

As for being activated: my recent experience with is mostly with RedHat-derived Linux server distributions (like CentOS), and they do come with the firewall enabled (which more than once made things not work until we noticed it was the firewall again). That didn't use to be the case in the distant past, however.