Greetings Gondarc, and welcome to the forum.

I am a LiveUSB user of Knoppix 6.7.1, but I've heard others say that one can have
problems doing an update/upgrade to Knoppix. Since Knoppix offerings are relatively frequent,
there are not many reasons to upgrade other than sparingly, say an application or a function here
and there.

Some problems arise out of the author's somewhat unique selection of program elements
across different repositories, and not being necessarily constrained to 'stable'.

Knoppix-firewall is an exception to the above. A new forum user like yourself found
the firewall menu item was not changeable. The author almost immediately posted a
correction in the debian-knoppix repository. This won't change the default, but will
allow you to do so if you want.

With a small LiveUSB install one can get into a lack-of-storage problem rather soon doing
a massive 'upgrade'.