I get your point. But in practice, how common is malware on linux systems. Maybe I am mistaken, but I have always felt this to be less likely there.
Less likely? Sure. Majority of malware probably isn't developed to target an operating system that's rarely used by 'stupid' people* (I.E. people who'd run "SuperHotPorn.jpg.exe" from the newsgroup a.b.erotica), and, an operating system that controls a shit ton less market share than it's buddies Macintosh and Windows.
Impossible? No.
*Yes, I realize there are pieces of malware out there that spread via exploits in popular 'open'/'public' software (Such as service daemons) and for that reason specifically target the operating system that runs the faulty software (And, in most cases, that'd be *NIX), but, I feel that the majority of malware is spread via items such as torrents and dodgy web-downloads, rather than actually specific exploits in applications to run executable code smuggled in from the outside.
