Better late than never.
This webpage gives a view on malware, already written for Linux, including the AV-scanners for Linux.
Linux malware - Wikipedia, the free encyclopedia
Linux is safer at this moment, but this won't last forever. Linux is becoming more and more popular and that makes Linux an interesting target for malware-writers.
In fact Linux is even more dangerous, because every Linux-users thinks nothing can hurt him and that's why a malware will longer survive on a Linux-computer.
If Linux was used by 85% of the world, Linux would become a second Windows in no time. Linux won't stop malware-writers and they will find security holes in Linux one way or the other.
Any OS or software is vulnerable, it's a matter of being a target or not.
Firefox was in the very beginning the safest browser and there were many arguments why Firefox was very safe. Nowadays Firefox must be patched regularly to cover its security holes and keep it safe.
Firefox isn't the safest browser anymore, it's Opera now.
The same will happen to Linux. History always repeats itself, but people never seem to learn from the past.