How Office 2010 New Application Security Works

by on March 24th, 2010

As the security landscape has been changing, Microsoft Office has had the misfortune of becoming one of the next big targets for hackers to attack. They have been going after many file-format parsers and how we read Office files. They’re looking for ways to exploit bugs and to get their code running on your machine. Microsoft have done a lot of work to find and fix bugs. Microsoft have to take a more proactive approach and build Office to be more resilient to attack. To do that, Microsoft has designed what they have been referring to as a new security workflow, a layered defense that Office documents have to go through as part of the File Open process. Microsoft is trying to make this process as invisible as possible.

Improved File Block

The security workflow they designed has several key features that they believe achieves the goals. First, they have improved File Block feature that was introduced in Office 2007. They can configure it in the application and have a finer level of granularity to manage how Word, Excel, and PowerPoint open their file types.

Office File Validation: Integral and Non-Intrusive

Another feature is new binary file-validation system, which call Office File Validation. Vast majority of the exploits have focused on older file formats, pre-dating XML versions, they built a system that can validate those files to make sure they conform to the documented format, before they are opened by Word, Excel, or PowerPoint. This is something Microsoft did in Publisher 2007, which worked out pretty well. Office File Validation is an integral part of Office that on most days, you would never know exists.

The next question is ‘What do you do with those blocked or invalid files?’. If Office just blocked a file and said it was invalid, you would probably be pretty curious why it was invalid, or if maybe Office program made a mistake. Or, you may be sure you know what it is, and still need to read it. Denying you access to these files doesn’t really meet Office goals, so they also built another system called as Protected View.

Office Protected View (more security, less annoyance)

Protected View is a way for Office to show Word, Excel, and PowerPoint files to you, but without all of the worry about those files being dangerous. They build up a read-only view of the document in an isolated sandbox, which has minimal access to the system, and no access to your other files and information. Even if the file is malicious, it can’t get out of the sandbox and do harm to your computer or data.

By tying all of these features together into a layered defense, any file that reaches your machine will get inspected for the file format being blocked, tested for validity, and shown in a read-only protected state. All this happens in real time, with an indistinguishable performance impact on your load time, and you can open these Office files without worry.

Microsoft’s other goal to make these features and workflow successful is that they don’t get in the way and instead have a positive impact on your experience. That means fewer dialog boxes and less information that is not actionable. They aer making security smart enough to get out of the way when its job is done. To do that, they have made files that open in Protected View remember when you chose to trust them, so you don’t have to re-trust them next time. You are not less secure; you’re just less annoyed by this.

How is your Microsoft Office 2010 Experience?


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