GNU/Linux is not a security panacea. It can be cracked, too.
Guess what? Nothing is certain except death and taxes.
But I have NEVER in 18 years had a virus on my linux box. I have never had anyone hack one, well, I take that back, one one time because I didn’t set ANYthing up on it and set it up to be hacked...
I have NEVER had a machine touched on my network behind a properly set up fire wall, but most importantly NEVER had a virus, and no, you can’t crack my machines.... and I doubt anyone can.
Oh...that's right...there aren't any.
Nothing is 100% secure if it is used.
But there is a vast difference between Linux and Windows when it comes to vulnerabilities from viruses.