I have a couple of inactive "slots" in my subscription, and have an old G5 Mac tower which I use for storing photographs and other archives. It runs OSX 10.5.8. Unsurprisingly, as it's a Power PC (pre Intel) device, current Norton software won't run on it. It's not switched on very often, so is unlikely to be a vector for malware which might affect the rest of my network. Is there anything I can do to protect it, or is it so unlikely to be a target that I can ignore the risk?