Hi killingtime,
there is no default password.
You can run
sudo passwd
to set one.
To make this persistent, you would need to add some files to /opt/.filetool.lst
etc/sudoers
etc/passwd
etc/shadow
etc/group
etc/gshadow
(this may be more than needed - not exactly sure)
and refresh your backup.
filetool.sh -b
AFAICT, by default, there are no network services running anybody could use to connect to your box and do bad things (ssh, samba, etc.).
However, you can install iptables.tcz on-boot and run /usr/local/sbin/basic-firewall via /opt/bootlocal.sh as described in iptables.tcz.info (can be viewed with the Apps GUI or tce-ab ).