No Operating System (OS) is "immune." But linux users are a rare bunch and viruses written for this OS are very rare. You will probably never see a virus, nor need anti-virus because of this lack of interest by attackers. Should a skilled attacker become individually interested with you, then I don't want you to think that linux is impervious. A lesson naive MAC users are learning now.... Although it is harder to get infected, don't for a moment imagine that Linux is invulnerable to viruses, worms, rootkits or anything else that's out there. As a matter of fact, your attitude and assumption that it is impossible to get infected if you use Linux is the greatest security hole in the whole system.