Give it a whirl, and you may be just as surprised as we were to learn that your ‘Downloads’ directory is taking up half your hard drive. Create a Reliable backup To create a bootable backup of your main drive there is only one choice, Carbon Copy Cloner, and it’s push one button simple.
Just remember to make your backup drive bootable, you will have to completely wipe your destination drive.
The problem is Apple hasn't officially announced its intention to send Snow Leopard to a nice farm with a new family.
In the case of the "gotofail" bug, which was caused by an errant line of C code that had been duplicated, the hole was in Mavericks and in i OS 6/7, but in the 10.9.2 update a patch for Safari also addresses "multiple memory corruption issues" in Web Kit (upon which Safari is based).
So the good news is that your older Snow Leopard machine doesn't have this latest exploit to begin with.
If you need more detail, the fantastic Take Control series has a pair of new PDF ebooks to guide you through the Snow Leopard installation: “Take Control of Upgrading to Snow Leopard” () and “Take Control of Exploring & Customizing Snow Leopard.” ().
post clarified regarding the "gotofail" bug, which is not present in Snow Leopard and did not require a security patch.