SSHGuard looks cool, wasn't aware that existed. Haven't messed with FreeBSD jails, but I use unprivileged lxc containers on Linux, iirc that's the closest Linux equivalent? Those help me sleep better at night.
Now I think lxd is supposed to be a better user experience than lxc. Same backend better frontend. Like ezjail or iocage for FreeBSD makes the management easier than doing it all directly.