fannymites, contrary to what many believes, SID does have the security updates/patches. These come in the form of new package releases either from upstream or via the Debian maintainers or nmu uploads. Unless you are one of those unlucky few not to have access to broadband, it is part of Best Housekeeping practices to update/upgrade your install every 2-3 days. To be absolutely honest, tons of things can happen in those 2-3 days but it is far better than doing no upgrades (not just for new spiffy features to installed apps but the security fixes that accompany the new releases to these installed apps). Everyone on the Net (or Interweb as Jono Bacon, Mark Revell and co. on lugradio will have it) has a role to play in keeping script kiddies and black hats at bay and thus a safer surfing experience for all.
While what has been suggested may not provide you or others 100% foolproof security (nothing ever will even in the forseeable future, unless you cast your box in cement and has it dumped 30, 000 feet underneath the deepest ocean), some security is better than no security. Believe me the Debian Security Team are a very hardworking lot, perhaps maybe too much free time on their hands or maybe simple paranoia but they are very meticulous in scanning source code to packages line-by-line looking for theoretical exploits and deriving effective patches for them and other security issues detected by others (e.g. other distros, securityfocus, etc).
As to whether installing a new release to Kanotix over an older one will imperil additional stuff that you've installed and personal files created since the last time, well, as far as I can recall (not touched Kanotix for almost 10 months now, last time I evaluated it was that long ago), I believe it has yet to provide an option at HD install time to upgrade an existing install. So unless, you have your /home on another partition, in all likelihood your existing Kanotix partition/install would be wiped clean by installing a new realease of Kanotix.
