As a Mac user and an information security expert, one of the most common questions I am asked these days is wether or not it is safe to run Windows on the new Intel-based Macs. Assuming people have generally accepted the poor state of desktop security, I suppose the real question they mean to ask is whether or not a vulnerability on the Windows side could impact the Mac side.

The short of my answer is that yes, it could. Although the operating systems run in different partitions (simplifying it here) of the hard drive, there is no theoretical reason why someone could not create a low-level piece of code on either side to access any random portions of the drive and thus impact the other.

As you may know, there are essentially two ways to run Windows on a Mac: a dual-boot configuration (e.g. with Apple's BootCamp) or through a Virtual Machine (VM) such as VMWare or Parallels. Either way presents certain risks. While I usually recommend virtualization as a security measure, the security posture of a system using a VM is only as good as the VM itself. Flaws in Sun's Java Virtual Machine, for example, have allowed Java code to impact the entire system in the past. In general, though, Java maintains an enviable security position.

Think of it this way - if the pilot of a 747 could download his own screen saver and open files from his email on the same computer as the flight systems, would you get on that plane? Your instinct is telling you that's laughably dangerous, and that you'd sooner cover your face in fresh meat and try and kiss a hungry Hyena. Your instinct is right. Anytime you run untrusted or unverified arbitrary code on any system, no matter how secure that system is, the entire system is now possibly compromised.

So are you too scared to run Windows now? Actually, despite what I've told you, your fears are unfounded. That's because there really isn't any compelling evidence to suggest that your Mac is more secure than Windows to begin with. (Let the flaming begin - I've already set up a filter.)

I know that sounds odd coming from a devout Mac advocate, but (especially) to an important question like this in my field, I want to give an answer based on facts, and not opinions.

Lets, the two of us, take a trip down a meandering stream of consciousness and enjoy a tour of the Macintoshes and Microsoft security, shall we?

There is a long list of reasons why I use the Mac over a PC. Most of them have to do with a user interface that's a joy to use, with beautifully rendered, anti-aliased text. If, like me, you need to stare at a lot of text all day, be it code or prose, there's zero doubt the Mac is superior. It simply works better; yes - that's a subjective statement.

And subjectively, I feel that, based on my knowledge of the systems in question, the Mac is more secure. Security, however, should not be considered subjectively, and so it's not on my afore mentioned long list of reasons why I love the Mac.

So why does the Mac "feel" more secure? Why are there ten viruses a day for the PC vs. less than ten ever for the Mac? Back up a second.

The reason people want to run Windows on their Mac is usually because there is some Windows-only software that the Mac user wants to run. The compiler and IDE that I use on my current project, for example, has Linux and Windows versions, but no Mac OS X version. The reason these tools, and indeed countless other software products, are available for Windows is that Windows is simply more popular.

And it is, in part, for that very reason why Windows appears to be less secure. Due to its large install base, it makes a more attractive target to hackers. If you're an evil maniac bent on destroying the world and you invent a way to poison fruit, you would poison the mangos first before the apples. That's because the mango is the world's most popular fruit. So if you're an evil maniac bent on spreading a computer virus, you would pick Windows over the Apples because Windows is the most popular desktop computer operating system. It's simple numbers - you're just trying to do the most damage.

In fact, during my time in a research group, I had a colleague who, upon reading the latest virus announcement which always seem to end in something like "Apple systems are not impacted" would also say, "go market share!" As astute of an observation as it is funny.

Mac OS X's BSD roots, as well as some good foresight from Apple on features like requiring admin passwords even when logged in as an administrator to access certain system configuration options, does help to make OS X more secure than it's Windows cousins in many areas. Features like the ability to encrypt your user folder and secure virtual memory also put Apple ahead. I should point out, though, that Vista is promising better user data encryption, and I have worked on embedded systems that used secure virtual memory since long before there was such a thing as Mac OS X.

So can Windows on an Intel Mac affect the OS X side? Probably; and in the security world, probably means yes. You simply need to take the same precautions you do with running Windows anywhere on your network. Running Windows in a VM may help, because you can always start from a disk and memory snapshot of a fresh install, read your virus infested emails, then quit the VM without permanently altering the state of Windows. It's not a perfect solution, but it's likely to be safer than allowing Windows to run for as long as it wants to and modify any files it sees fit to.

Finally, is OS X more secure than Windows? For now. Probably. What's more important is that with Windows targeted first over the Mac, the Mac is "safer," even if it's no more "secure." What does "more secure" mean? How is it measured? It better not use statistics, right? We'll tackle all this next time.