Changes in Windows to Meet Changes in Threat Landscape

Customers have heard us say over the years that the threat environment is an ever-evolving one. That means that one of our jobs in working to keep customers safe is to continually monitor the threat environment and make changes to adapt to it.

Today, we’re announcing modifications in Windows that adapts to recent changes in the threat environment. Specifically, we’re announcing changes to the behavior in AutoPlay so that it will no longer enable an AutoRun task for devices that are not removable optical media (CD/DVD.). However, the AutoRun task will still be enabled for media like CD-ROM. There are more details on the change over at the Windows 7 blog as well as at the Security Research and Defense (SRD) blog.
The reason we’re making this change is that we’ve seen an increase, since the start of 2009, in malicious software abusing the current default AutoRun settings to propagate through removable media like USB devices. The best known malicious software abusing AutoRun is Conficker, but it’s not alone in that regard: there is other malicious software that abuses this feature. You can get more details on this change and others in the threat environment from the Microsoft Malware Protection Center’s blog.

Because we’ve seen such a marked increase in malicious software abusing AutoRun to propagate, we’ve decided that it makes sense to adjust the balance between security and usability around removable media. We’ve tried to be very measured in this adjustment to maximize both customer convenience and protection. Since non-writable media such as CD-ROMs generally aren’t avenues for malicious software propagation (because they’re not writable) we felt it made sense to keep the current behavior around AutoPlay for these devices and make this change only for generic mass storage class devices.

This change will be present in the Release Candidate build of Windows 7. In addition, we are planning to release an update in the future for Windows Vista and Windows XP that will implement this new behavior.