u really don't need a virus guard if you use carefully. Don't always keep your Bluetooth on. Don't plug to the PC's if you have doubt that it has virus. here are some articles http://www.rediff.com/money/2006/feb/08spec1.htm
if u nt browsing web,pc communication o bluetooth communication u really dnt wanna hv 2..buh sm of pc viruses dnt effect to ur mobile..if u using a simbian 4n itz gud 2 install a virus gurad..