As mentioned before on this blog (regarding our UAC changes) and on the IE blog (regarding the SmartScreen® filter for malware), we have an increased focus to enable customers to be in control and feel confident about the software that they choose to run on their computers. Folks on this blog have also commented about the concerns they have specifically in the AutoPlay area. This blog entry addresses some of the changes that we have made to increase customer confidence when using their media and devices with Windows. It is authored by Arik Cohen, a program manager on the Core User Experience team. –Steven [Note: There was a technical problem so this post was reposted in its entirety.]
Certain malware, including the Conficker worm, have started making use of the capabilities of AutoRun to provide a seemingly benign task to people – which masquerades as a Trojan Horse to get malware onto the computer. The malware then infects future devices plugged into that computer with the same Trojan Horse. For further information about Conficker please visit http://www.microsoft.com/protect/computer/viruses/worms/conficker.mspx
In the following example for a USB flash drive that has photos, malware registers as the benign task of “Open folders to view files.” If you select the first “Open folders to view files” (circled in red), you would be running malware. However, if you select the second task (circled in green), you would be safe running the Windows task.
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Infected USB AutoPlay
People are confused why they have two tasks that appear to do the same thing – and even a knowledgeable person who is careful not to run software from an untrusted source can easily make the mistake of selecting the first task. As a result, people lose confidence and don’t feel in control.
A growing attack
While presenting an AutoRun task in AutoPlay has been available since Windows XP, we have seen a marked increase in the amount of malware that is using AutoRun as a potential method of propagation. According to the Security Intelligence Report, an enterprise study by Forefront Client Security found that the category of malware that can propagate via AutoRun accounted for 17.7% of infections in the second half of 2008 – the largest single category of malware infections.
The chart below shows the increasing amount of detection reports by Microsoft anti-virus software of the class of infections that spread via AutoRun. (Note: The actual method of infection cannot be determined.)
Currently, disabling AutoPlay completely is the only solution for consumers and enterprises to gain confidence with the use of USB flash devices on their computer. Guidance on disabling AutoPlay is available here.
Infection Detections of Malware that Spread via AutoRun
Increasing customer confidence
Windows 7 introduces key changes to AutoPlay that keep you from being exposed inadvertently to malware like Conficker when doing your common scenarios with devices (e.g., get to the files on your USB flash drive, download pictures from an SD card, etc.).
In particular, Windows will no longer display the AutoRun task in the AutoPlay dialog for devices that are not removable optical media (CD/DVD.) because there is no way to identify the origin of these entries. Was it put there by the IHV, a person, or a piece of malware? Removing this AutoRun task will block the current propagation method abused by malware and help customers stay protected. People will still be able to access all of the other AutoPlay tasks that are installed on their computer.
With these changes, if you insert a USB flash drive that has photos and has been infected by malware, you can be confident that the tasks displayed are all from software already on your computer:
On the other hand, if you insert a CD that offers software to install, Windows will still display the AutoRun task provided by the ISV during their media creation process. For example:
Infected USB AutoPlay after AutoPlay changes
You will first see this updated AutoRun experience in the Windows 7 RC build, and we will be bringing this change to Vista and XP in the future.
AutoPlay for a CD that offers an AutoRun Task
Ecosystem Impact
We are working with our ecosystem partners to help mitigate situations where this AutoRun change will have an impact on them.
CDs and DVDs (including CD emulation), where the IHV specified AutoRun task authored during manufacturing, will continue to provide the AutoRun choice allowing customers to run the specified software. IHVs of generic mass storage devices should expect that people will browse the contents of the device to launch any software. The new behavior will allow customers to continue to use AutoPlay (including all Windows and ISV installed tasks) to access their media and devices while not being presented with tasks from malware. Additionally, device classes, such as portable media players and cell phones, now support Device Stage™ on Windows 7. DeviceStage offers the IHV a multifunction alternative to AutoPlay where they can present links to software and common tasks, and provides additional features as you use the device.
As you try out the Windows 7 RC, we hope these changes will make you feel more confident and in control when using your media and devices.
-Arik Cohen
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