I use Norton AV myself. There's also Virex which has been popular on macs for many years (& is on a G3 here.) That's all I know for mac without searching for them. I was under the impression the mac Norton AV would also detect pc viruses. It gets updated every week yet there's so very few known OSX viruses. In fact I just checked thru the virus definitions & 99% say pc viruses.

As far as using Norton AV, I use it manually. I can afford to do that on a mac. Just periodically doing full partition checks. Generally I'll just check individual folders. That is ideal for LW.