Files changed with no notice to users

In recent days, Windows Update (WU) started altering files on users' systems without displaying any dialog box to request permission. The only files that have been reportedly altered to date are nine small executables on XP and nine on Vista that are used by WU itself. Microsoft is patching these files silently, even if auto-updates have been disabled on a particular PC.

It's surprising that these files can be changed without the user's knowledge. The Automatic Updates dialog box in the Control Panel can be set to prevent updates from being installed automatically. However, with Microsoft's latest stealth move, updates to the WU executables seem to be installed regardless of the settings — without notifying users.

When users launch Windows Update, Microsoft's online service can check the version of its executables on the PC and update them if necessary. What's unusual is that people are reporting changes in these files although WU wasn't authorized to install anything.

This isn't the first time Microsoft has pushed updates out to users who prefer to test and install their updates manually. Not long ago, another Windows component, svchost.exe, was causing problems with Windows Update, as last reported on June 21 in the Windows Secrets Newsletter. In that case, however, the Windows Update site notified users that updated software had to be installed before the patching process could proceed. This time, such a notice never appears.

For users who elect not to have updates installed automatically, the issue of consent is crucial. Microsoft has apparently decided, however, that it doesn't need permission to patch Windows Updates files, even if you've set your preferences to require it.

Microsoft provides no tech information — yet

To make matters even stranger, a search on Microsoft's Web site reveals no information at all on the stealth updates. Let's say you wished to voluntarily download and install the new WU executable files when you were, for example, reinstalling a system. You'd be hard-pressed to find the updated files in order to download them. At this writing, you either get a stealth install or nothing.

A few Web forums have already started to discuss the updated files, which bear the version number 7.0.6000.381. The only explanation found at Microsoft's site comes from a user identified as Dean-Dean on a Microsoft Communities forum. In reply to a question, he states:

System logs confirm stealth installs

In his forum post, Dean-Dean names several files that are changed on XP and Vista. The patching process updates several Windows\System32 executables (with the extensions .exe, .dll, and .cpl) to version 7.0.6000.381, according to the post.

In Vista, the following files are updated:

1. wuapi.dll
2. wuapp.exe
3. wuauclt.exe
4. wuaueng.dll
5. wucltux.dll
6. wudriver.dll
7. wups.dll
8. wups2.dll
9. wuwebv.dll

In XP, the following files are updated:

1. cdm.dll
2. wuapi.dll
3. wuauclt.exe
4. wuaucpl.cpl
5. wuaueng.dll
6. wucltui.dll
7. wups.dll
8. wups2.dll
9. wuweb.dll

These files are by no means viruses, and Microsoft appears to have no malicious intent in patching them. However, writing files to a user's PC without notice (when auto-updating has been turned off) is behavior that's usually associated with hacker Web sites. The question being raised in discussion forums is, "Why is Microsoft operating in this way?"

How to check which version your PC has

If a system has been patched in the past few months, the nine executables in Windows\System32 will either show an earlier version number, 7.0.6000.374, or the stealth patch: 7.0.6000.381. (The version numbers can be seen by right-clicking a file and choosing Properties. In XP, click the Version tab and then select File Version. In Vista, click the Details tab.)

Step 1. In XP, click Start, Run.

Step 2. Type eventvwr.msc and press Enter.

Step 3. In the tree pane on the left, select System.

Step 4. The right pane displays events and several details about them. Event types such as "Installation" are labeled in the Category column. "Windows Update Agent" is the event typically listed in the Source column for system patches.

On systems that were checked recently by Windows Secrets readers, the Event Log shows two installation events on Aug. 24. The files were stealth-updated in the early morning hours. (The time stamp will vary, of course, on machines that received the patch on other dates.)

To investigate further, you can open the Event Log's properties for each event. Normally, when a Windows update event occurs, the properties dialog box shows an associated KB number, enabling you to find more information at Microsoft's Web site. Mysteriously, no KB number is given for the WU updates that began in August. The description merely reads, "Installation Successful: Windows successfully installed the following update: Automatic Updates."

No need to roll back the updated files

Again, it's important to note that there's nothing harmful about the updated files themselves. There are no reports of software conflicts and no reason to remove the files (which WU apparently needs in order to access the latest patches). The only concern is the mechanism Microsoft is using to perform its patching, and how this mechanism might be used by the software giant in the future.

I'd like to thank reader Angus Scott-Fleming for his help in researching this topic. He recommends that advanced Windows users monitor changes to their systems' Registry settings via a free program by Olivier Lombart called Tiny Watcher. Scott-Fleming will receive a gift certificate for a book, CD, or DVD of his choice for sending in a comment we printed.

I'll report further on this story when I'm able to find more information on the policies and techniques behind Windows Update's silent patches. Send me your tips on this subject via the Windows Secrets contact page.