:ph34r: Linux is "virus-free" in that there are essentially no viruses for Linux in the wild, although research viruses certainly do exist. It is also "virus-free" for much the same reason as vendors give for not porting closed-source apps to it - the number of permutations is high, so the number of machines a closed-source program will run on (unless libraries are included) is relatively low. (Vendors don't have the excuse virus-writers have of wanting to keep the binaries small and are quite capable of supplying statically-linked binaries or the shared libraries with a suitable LD_LIBRARY_PATH - and some do.) There are other reasons, of course. "Normal" user accounts have much more limited access to the rest of the system, so making the corruption of system binaries much harder. Many distributions provide intrusion-detection software for detecting binary changes. Distributions release regular updates, which means a virus will be overwritten in a relatively short timeframe. Mandatory access controls are becoming more popular, limiting what a virus can do even if it did infiltrate a system binary. And so on. BIOS viruses are OS-independent and so a potentially greater threat. The flash memory is usually unscanned by virus scanners, as well. However, BIOS viruses have had something like ten years to emerge and really haven't been as much of a problem as initially predicted. With the increasing popularity of flashable firmware and "intelligent" devices and daughter cards, you'd expect to see problems there too, but that's so far not happened. Having said that, because flash content is updated far less often, requires nothing to stay in verified areas of the system, and requires there to be only a temporary exploit, I would expect to see these becoming a problem for Linux users long before true native Linux viruses themselves will be. pasted from a techy site!