As Ive written just a few months ago, the problem of the old Office file formats is perhaps the biggest security challenge for Microsoft. Even if Office 2007 and its new formats are a real solution, it will take years before adoption of the new version is dominant.
Thats why MOICE (Microsoft Office Isolated Conversion Environment) is such a good idea, and why Im perplexed at the failure of some people to get the point of it. Our own Joe Wilcox expressed incredulity at every claim for it recently in his blog.
If you need a terse and clear explanation of what MOICE does, read MS Knowledge Base article 935865 (where you can also download MOICE):
What does this accomplish? It prevents Office-based malware authors from using the old formats to attack Office users. The MOICE program that does the actual conversion needs and runs with very few privileges. It only needs read and write access to the directory in which it operates. It doesnt need permission to execute external programs, for example, so if an attacker were to write a Word document that compromised MOICE, then there isnt much they could do with it. This is why the term "sandbox" has been used.
Its easy to presume that Microsoft has ulterior motives for MOICE, and perhaps they even consciously see it as a way of promoting the use of Open XML, or at least of making users feel more at ease with it. So what? This is objectionable only of youre trying to oppose Microsoft for the sake of opposing Microsoft, and it doesnt dispute the obvious security benefits of MOICE. And just in case theres any confusion about this, MOICE does not require the user to run Office 2007 at all; along with the Office 2007 format support for Office 2003, its a solution for Office 2003 users.