Avast has antivirus for Linux, free for home use :
http://www.avast.com/eng/avast-for-l...rkstation.html
About getting knowledge about Linux security, I think the best resource would be to get hold of freely available e-books on Linux, or posting the concerned question on the Linux forums. There are quality material available for reading about Linux, ranging from a novice to an expert level. Serious Linux users should read these books. There is so much to learn about Linux... and its fun too.