Engineering Windows 7

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Update on UAC

Update on UAC

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Hi, Jon DeVaan here to talk to you about the recent UAC feedback we’ve been receiving.

Most of our work finishing Windows 7 is focused on responding to feedback. The UAC feedback is interesting on a few dimensions of engineering decision making process. I thought that exploring those dimensions would make for an interesting e7 blog entry. This is our third discussion about UAC and for those interested in the evolution of the feature in Windows it is worth seeing the two previous posts (post #1 and post #2) and also reading the comments from many of you.

We are flattered by the response to the Windows 7 beta so far and working hard at further refining the product based on feedback and telemetry as we work towards the Release Candidate. For all of us working on Windows it is humbling to know that our work affects so many people around the world. The recent feedback is showing us just how much passion people have for Windows! Again we are humbled and excited to be a part of an amazing community of people working to bring the value of computing to a billion people around the world. Thank you very much for all of the thoughts and comments you have contributed so far.

UAC is one of those features that has a broad spectrum of viewpoints with advocates staking out both “ends” of the spectrum as well as all points in between, and often doing so rather stridently. In this case we might represent the ends of the spectrum as “security” on one end and “usability” on the other. Of course, this is not in reality a bi-polar issue. There is a spectrum of perfectly viable design points in between. Security experts around the world have lived with this basic tension forever, and there have certainly been systems designed to be so secure that they are secure from the people who are supposed to benefit from them. A personal example I have, is that my bank recently changed the security regimen on its online banking site. It is so convoluted I am switching banks. Seriously!

Clarifying Misperceptions

As people have commented on our current UAC design (and people have commented on those comments) it is clear that there is conflation of a few things, and a set of misperceptions that need to be cleared up before we talk about the engineering decisions made on UAC. These engineering decisions have been made while we carry forth our secure development lifecycle principles pioneered in Windows XP SP2, and most importantly the principle of “secure by default” as part of SD3+C. Windows 7 upholds those principles and does so with a renewed focus on making sure everyone feels they are in control of their PC experience as we have talked about in many posts.

The first issue to untangle is about the difference between malware making it onto a PC and being run, versus what it can do once it is running. There has been no report of a way for malware to make it onto a PC without consent. All of the feedback so far concerns the behavior of UAC once malware has found its way onto the PC and is running. Microsoft’s position that the reports about UAC do not constitute a vulnerability is because the reports have not shown a way for malware to get onto the machine in the first place without express consent. Some people have taken the, “it’s not a vulnerability” position to mean we aren’t taking the other parts of the issue seriously. Please know we take all of the feedback we receive seriously.

The word “vulnerability” has a very specific meaning in the security area. Microsoft has one of the leading security agencies in the world in the Microsoft Security Response Center (secure@microsoft.com) which monitors the greater ecosystem for security threats and manages the response to any threat or vulnerability related to Microsoft products. By any definition that is generally accepted across the world wide security community, the recent feedback does not represent a vulnerability since it does not allow the malicious software to reach the computer in the first place.

It is worth pointing out the defenses that exist in Windows Vista that keep malware from getting on the PC in the first place. In using Internet Explorer (other browsers have similar security steps as well) when attempting to browse to a .vbs file or .exe file, for example, the person will see the prompts below:

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Internet Explorer 8 has also introduced many new features to thwart malware distribution (see http://blogs.msdn.com/ie/archive/2008/08/29/trustworthy-browsing-with-ie8-summary.aspx ). One of my favorites is the SmartScreen® Filter which helps people understand when they are about to visit a malicious site. There are other features visible and hidden that make getting malware onto a PC much more difficult.

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A SmartScreen® display from IE 8

Additionally, if one attempts to open an attachment in a modern email program (such as Windows Live Mail) the malware file is blocked:

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Much of the recent feedback has failed to take into account the ways that Windows 7 is better than Windows Vista at preventing malware from reaching the PC in the first place. In Windows 7 we have continued to focus on improving the ability to stop malware before it is installed or running on a PC.

The second issue to untangle is about the difference in behavior between different UAC settings. In Windows 7, we have four settings for the UAC feature: “Never Notify,” “Notify me only when programs try to make changes to my computer (without desktop dimming),” “Notify me only when programs try to make changes to my computer (with desktop dimming),” and “Always Notify.” In Windows Vista there were only two choices, the equivalent of “Never Notify” and “Always Notify.” The Vista UI made it difficult for people to choose “Never Notify” and thus choosing between extremes in the implementation. Windows 7 offers you more choice and control over this feature, which is particularly interesting to many of you based on the feedback we have received.

The recent feedback on UAC is about the behavior of the “Notify me only when programs try to make changes to my computer” settings. The feedback has been clear it is not related to UAC set to “Always Notify.” So if anyone says something like, “UAC is broken,” it is easy to see they are mischaracterizing the feedback.

The Purpose of UAC

We are listening to the feedback on how “Notify me only when…” works in Windows 7. It is important to bring in some additional context when explaining our design choice. We choose our default settings to serve a broad range of customers, based on the feedback we have received about improving UAC as a whole. We have learned from our customers participating in the Customer Experience Improvement Program, Windows Feedback Panel, user surveys, user in field testing, and in house usability testing that the benefit of the information provided by the UAC consent dialog decreases substantially as the number of notifications increases. So for the general population, we know we have to present only key information to avoid the reflex to “answer yes”.

One important thing to know is that UAC is not a security boundary. UAC helps people be more secure, but it is not a cure all. UAC helps most by being the prompt before software is installed. This part of UAC is in full force when the “Notify me only when…” setting is used. UAC also prompts for other system wide changes that require administrator privileges which, considered in the abstract, would seem to be an effective counter-measure to malware after it is running, but the practical experience is that its effect is limited. For example, clever malware will avoid operations that require elevation. There are other human behavior factors which were discussed in our earlier blog posts (post #1 and post #2).

UAC also helps software developers improve their programs to run without requiring administrator privileges. The most effective way to secure a system against malware is to run with standard user privileges. As more software works well without administrator privileges, more people will run as standard user. We expect that anyone responsible for a set of Windows 7 machines (such as IT Administrators or the family helpdesk worker (like me!)) will administer them to use standard user accounts. The recent feedback has noted explicitly that running as standard user works well. Administrators also have Group Policy at their disposal to enforce the UAC setting to “Always Notify” if they choose to manage their machines with administrator accounts instead of standard user accounts.

Recapping the discussion so far, we know that the recent feedback does not represent a security vulnerability because malicious software would already need to be running on the system. We know that Windows 7 and IE8 together provide improved protection for users to prevent malware from making it onto their machines. We know that the feedback does not apply to the “Always Notify” setting of UAC; and we know that UAC is not 100% effective at stopping malware once it is running. One might ask, why does the “Notify me only when…” setting exist, and why is it the default?

Customer-Driven Engineering

The creation of the “Notify me only when…” setting and our choice of it as the default is a design choice along the spectrum inherent in security design as mentioned above. Before we started Windows 7 we certainly had a lot of feedback about how the Vista UAC feature displayed too many prompts. The new UAC setting is designed to be responsive to this feedback. A lot of the recent feedback has been of the form of, “I’ll set it to ‘Always Notify,’ but ‘regular people’ also need to be more secure.” I am sure security conscious people feel that way, and I am glad that Windows 7 has the setting that works great for their needs. But what do these so called “regular people” want? How to choose the default, while honoring our secure design principles, for these people is a very interesting question.

In making our choice for the default setting for the Windows 7 beta we monitored the behavior of two groups of regular people running the M3 build. Half were set to “Notify me only when…” and half to “Always Notify.” We analyzed the results and attitudes of these people to inform our choice. This study, along with our data from the Customer Experience Improvement Program, Windows Feedback Panel, user surveys, and in house usability testing, informed our choice for the beta, and informed the way we want to use telemetry from the beta to validate our final choice for the setting.

A key metric that came out of the study was the threshold of two prompts during a session. (A session is the time from power up to power down, or a day, whichever is shorter.) If people see more than two prompts in a session they feel that the prompts are irritating and interfering with their use of the computer. In comparing the two groups we found that the group with the “Always Notify” setting was nearly four times as likely to have sessions with more than two prompts (a 1 in 6.7 chance vs a 1 in 24 chance). We gathered the statistic for how many people in the sample had malware make it onto their machine (as measured by defender cleaning) and found there was no meaningful difference in malware infestation rates between the two groups. We will continue to collect data during the beta to see if these results hold true in a much broader study.

We are very happy with the positive feedback we have received about UAC from beta testers and individual users overall. This helps us validate our “regular people” focus in terms of the trade-offs we continue to consider in this design choice. We will continue to monitor the feedback and our telemetry data to continue to improve our design choices on UAC.

So as you can see there is a lot of depth to the discussion of UAC and the improvements made in Windows 7 in UAC itself and in improving ways to prevent malware from ever reaching a PC. We are working hard to be responsive to the feedback we received from Vista to provide the right usability and security for people of all types. We believe we’ve made good progress and are listening carefully to the feedback on our UAC changes. Again please accept our most sincere thanks for the passion and feedback on Windows 7. While we cannot implement features the way each and every one of you might wish, we are listening and making a sincere effort to properly weigh all points of view. Our goal is to create a useful, useable, and secure Windows for all types of people.

Jon

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  • I would like an option to keep expanded the Details shown in the UAC dialog box. Thanks

  • Would it be possible to add a simple check box, to allow the User to be notified if UAC level or setting was changed?

  • I think that the problem most people have isn't the default setting, but the fact that "Notify only when other applications..." doesn't actually work. Any application that is running can bypass this control and get as much access as if UAC wasn't running at all - not really a control is it?

    UAC may not be technically considered a "security boundary", but in Vista, in practical use it was very close. In Vista if you run a malicious application, it can only affect your user account unless you specifically and explicitly allow it to do otherwise. Windows 7 makes that same promise, but doesn't deliver - that same malware, if adapted to 7, can take over the whole box. Performing the same set of actions in 7 shouldn't result in a worse outcome [than in Vista].

    --

    Aside from that I haven't actually met anyone who has complained about UAC... other than from what they have seen on an Apple ad. Most people so infrequently install apps, that it doesn't affect them. Maybe my case is weird they don't have any misbehaving legacy apps. UAC has improved the quality of Windows applications and Microsoft should be applauded for that.

    If people want to take off their protection let them, but it's up to them to suffer the consequences.

    If you can't make the default setting do what it say it does in a rock solid fashion, just use the known good Vista approach. (Just like every other OS on the planet)

  • I think there it's still missing the point. It's a good balance to have the defaults as they are in the Windows 7 beta. The issue is making sure they stay that way.

    Having a prompt just for changing the UAC settings would be extremely unlikely to change the 2 per-session guideline (after all, you aren't going to be changing it often) but would prevent malware that has made it through the existing defences from changing the setting even lower.

    Just because it isn't a security vulnerabilty doesn't mean that it's behaviour makes sense.

  • While UAC may not be a security boundary, when the Operating System's default state allows any application to trivally have the System elevate arbitrary code, you no longer have a useful tool at all.

    And the sources of malicious code are far more than that downloaded via Internet Explorer or an attachment-minding email client.

    The long and the short of it is the token needed to adjust the UAC setting should be something above that granted by the autoElevate system.

  • Jon, you're missing the point. The people only want to see an UAC notification when the UAC level is changed. That's all.

    You don't have to change anything else.

  • I'm not sure you only have to protect the UAC level.  Does the default setting allow an application to do the following without any notification? ... only if Im an administrator or if Im a user?:

    Replace a windows .dll

    Uninstall a driver

    Change services

    Add executable to startup

    ... etc

    Assuming an app could do all of this silently, what good is UAC for at this point anyway.  Why not just remove it.

    -d

  • While I understand that you do not consider UAC the ultimate barrier against malware, even with all the new security barriers in mail, IM and IE8 you saw that it did not prevent for malware to be installed.

    So, a new barrier should be running to prevent the installed malware to harm the computer.

    Naturally, this barrier can be the UAC (although I'm pretty sure a lot of malware can run in user mode if its just collecting data..)

  • with all those REQUEST , become 40 SKU of Windows 7 :D

  • I think the point that it shouldn't be so easy for an application to elevate itself  hasn't been answered in the post. The comments so far explain the situation very well though, I don't see why microsoft don't want to remove or change the way auto-elevation works.

  • Look at it this way - let's say I let my son bring a friend over, even one who I thought was trustworthy.

    I dont need to be notified if he takes a drink from my fridge or sits on my chair.  But I'd REALLY like to be notified if he's trying to remove the locks to my bedroom door.

    The changing of the UAC setting itself must be an exception.  It is a fundamentally different setting than any other setting.  I simply dont understand how this is not painfully obvious.  If not for the reality of this situation, then for the perception.  If you guys are correct, the only people that should see this are people already infected with malware, so a second reminder that something really fishy is going on is not going to hurt.    

  • Wow. Wrong answer.

    The Microsoft response to this issue is really shaking my faith the quality of Windows 7.  Vista was full of the sort of obtuse thinking.  Every single person outside of Microsoft knows the fix for this, its mentioned multiple times in the comment in this thread.

    Put on your "common sense" hat and just fix the issue, guys.  It's not that difficult.

  • I think part of the issue here is the fact that there is an assumption that any untoward goings on will only ever be caused by malware or spyware.

    As far as Im concerned, no application trusted or otherwise, should be able to alter the core UAC settings without express permission from the user (via a UAC prompt). As it currently is in the beta, any application running on the system can very easily and silently disable UAC completely, thereby giving itself and any other app that wants it, full access to the system. That alone completely nullifies the point of having UAC or any other security boundary in the first place, if it can be so easily tampered with by any running process.

    I do agree with Microsoft's assertion that UAC was not specifically designed as a fool proof security barrier, but it is however an important part of Windows' security model and should be treated as such. As it currently is in the beta, it can be so easily disabled it may as well not be there at all. As others have pointed out, the default setting is fine (And works well) but there certainly needs to be some kind of prompt when attempting to change UAC's core settings.

  • Sometimes, inconsistency with your own ideals is a good thing.  Make an exception, if only to put people's fears to rest.

  • I see your point that the malware *should* never get onto the computer in the first place, but imagine if I downloaded a piece of software that unknown to me had malware piggybacking on it.  I would click through the UAC promts thinking I was installing a legit program, while in the background this program is also being installed.  Rafael Rivera's list of EXE's that can be evelevated without promting UAC is sligtly scary!  All you would have to is prompt when the UAC level changes or is changed.

    Just another UI idea for UAC, a checkbox with "Don't prompt UAC for This Program Again."  would be HUGE!  The list of allowed programs could be managed in the control panel.

    Anyway, thanks for all your work on UAC!

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