mac osx 10.5 virus protection

hi, i was wondering what is the best (preferably free) antivirus software for my macbook pro. the only reason is because i have about 6-7k of software on my macbook pro and it would be a royal pain in the ***** if i got a virus. also can anyone recommend a portable external hard drive i can back up my internal hard drive on to. (cheapish one plz) thanks about 200gb would do

THere are no viruses that infect OSX, and only a handful of trojans that you would have to be foolish enough to manually download and install

If you really need to do a scan then the free ClamX will do that for you

Otherwise, read the Antivirus and firewall sticky for more on mac security
http://www.mac-forums.com/forums/switcher-hangout/23835-official-mac-antivirus-firewall-faq.html