Here’s a screenshot of a website for Windows XP:

(Trojan in Windows XP.)
There is an animation of a Windows scanning utility discovering lots of trojan, an anti-spyware tool would be offered at the end. It tricks users into install something that they claim secure.
Here’s the same website in Ubuntu with the same animation:

(Trojan in Ubuntu.)
The screenshot would probably look realistic to a naive Windows XP user. And when you install the additional checking tool, who knows, you may end up with a virus.
I tried installing it in Ubuntu and couldn’t. Me sad.
[Thanks Irene for showing me the site.]







