Antivirus no Firewall yes, Look up Iptables which is for firewalling, Documentation can be found using the man command in a terminal window
The easiest way to use iptables is to use a gui like firestarter, click here It does a great job but needs to be ran as root, So open a terminal and su to root and type firestarter once you have it installed obviousley :)
The number of viri for linux is extremely small probably countable on both hands, Even if you did manage to get one as long as you werent logged into your PC as root the damage would be minimal because it wouldnt be able to touch any file other than the ones a user has access to. Usually /home/paul
This thread is now locked and can not be replied to.