Im quoted in April 6s USA Today in its story about Boot Camp, Apples new software support for running Windows on Intel-based Macs. The reporters question to me was whether Windows malware could attack the Macs running Windows.
Of course, the answer is, “Of course.” Unless Apple has pulled off some secret miracle, any malware targeted at Windows will run on an Apple computer running Windows.
The more interesting question is whether it could affect the Mac parts of the system.
At first it seemed to me that this was theoretically possible, but highly unlikely, both for technical and practical reasons.
My understanding from talking to people who (unlike me) have actually used Boot Camp is that it is a simple boot loader. The Windows and Mac file systems exist on the system in separate hard disk partitions. From what Ive read, they dont see each other, at least not by default.
There is no software currently included to make Windows see the Mac partition. Perhaps this will be addressed by third parties.
But it is also my understanding that nothing in Boot Camp prevents Windows from reading the portions of the disk that contain the Mac file system, and this is where the Mac becomes vulnerable.
It should be possible for a malware writer to write a Mac OS X infection program inside a Windows program that will a) determine that it is running on a Mac, b) find the partition with the Mac file system, c) include code for basic file I/O on it and d) infect it.
In fact, once a, b, and c are done, d is really tempting, because infecting a Mac system under OS X is not easy. This scenario proves the old truism that without physical security there is no security at all. However, it also largely proves the old and much-maligned adage of “security through obscurity,” as its hard to see any malware writer actually going through the trouble of doing this.
It would involve an great deal of work. But maybe not as much as you might think. The source code for Darwin, which is the basis of the Mac OS X, is available out in the open, and my understanding is that the basic file system code is in there. A malware writer could include the code, or a derivative thereof, in the program.
This type of Windows malware would be able to read and write the offline OS X partition completely bypassing all the OS X security, because OS X would not be running at the time.
If it were sophisticated enough about using the file system, it could write malware into the OS X installation fully installed. Getting theoretical here, it might even be possible to replace parts of the Mac operating system with malicious versions.
So, is this going to happen? For all the same reasons that little or no malware exists for the Mac, there is even less reason to write this program. If youre a malware writer you want your program to spread. The odds of a Windows system running this program are high, but the odds that the Windows system will be an Intel-based Mac running Boot Camp are very low.
There are things that could be done, like disguise it as a special Windows-based Boot Camp utility, perhaps one that gives file system access to the Mac partition. When these utilities come out, make sure to get them only from trustworthy sources.
Security Center Editor Larry Seltzer has worked in and written about the computer industry since 1983. He can be reached at firstname.lastname@example.org.