Your Mac is safe from viruses. But your data on it are not.

Today I'd like to talk a bit about one of the biggest misconceptions about the Mac: the idea that it is somehow inherently safe against viruses.

First: I'm a happy Mac user, typing this blog on my Powerbook G4, and I consider Steve a genius and Bill, well, not. So having made clear that I'm not writing this out of "Bill fanboyism" let's take a look at what malware can do on a Mac.

In my opinion it is true that MacOS X is inherently more safe against viruses as Windows is. A major reason for that might be the fact that MacOS X is, in its heart, a Unix, and Unix has been built with multiple users in mind, while Windows has not. If you're writing a multi-user operating system, one of your chief tasks is to protect one user from the stupidity of the other user. Unix is really good at that, and Apple has been careful to give the (typically one and only) MacOS user only a little bit of additional control. If you install a piece of software that needs to break the security barrier down to the OS files which are also used by others, Mac OS X tells you that clearly and allows only this installation process to do that. In Windows (at least in XP, not tried Vista yet which obviously is imitating MacOS X in this respect), nearly everybody I know has set his own user's rights to "Admin" after some struggling with Installers. Bad idea from an OS point of view.

Okay, let's assume it's fairly safe to say that MacOS X is more or less well protected against viruses (the "month of apple bugs" has proven that there are not too many holes)...

But does this mean that you, as a Mac user, are protected against viruses?

The answer is no. It only means that your girlfriend, dad, and whoever else happens to have another account on your Mac, and the OS itself is protected against viruses you've let in. So let's imagine you get a mail with an executable as an attachment. The executable will, if run, delete all files it can find (no, that's not a virus, but it gets the point across). Since you've got - in our imagination - a severe hangover right now you click on the executable.

What will happen in this situation? That's easy to answer: all your files get deleted, all the others' files and all the OS-owned files stay protected. Nice from an OS point of view, not nice from your point of view.

Similarly, if you install software with security holes on your computer, all your personal data are in danger while this software is running. And there's not a thing Mac OS, Windows or Linux can do about that. And even if you do regular backups, all the files there might be similarly in danger. The only thing that could help against this kind of problem is an operating system that would put programs downloaded from the web into separate sandboxes that can't affect each other without a similar permission as the one MacOS X grants for doing administrative things. But no operating system I know does this out of the box.

My conclusion: if you are a Mac user, don't feel too safe and protected from viruses. Trust your Mac OS. Don't trust software you've downloaded from the web. Think before you run software. Your OS may be rather safe from viruses. But your files are not. And at least in my case, restoring my OS from scratch and installing my applications again costs me a day; the really precious stuff on my Mac are my documents, my photos, my music.