What is Wuauclt.exe

Windows Update - Microsoft® Windows® Operating System - Microsoft Corporation

File description

Wuauclt.exe with description Windows Update is a process file from company Microsoft Corporation belonging to product Microsoft® Windows® Operating System.
The file is digitally signed from Microsoft Windows Component Publisher - Microsoft Timestamping Service
We do not recommend removing digitally signed files from Microsoft Windows Component Publisher

What is wuauclt.exe?
Wuauclt.exe is the Windows Update Autoupdate Client. It is a background process that periodically checks with Microsoft's servers for updates to the operating system and drivers.

If you wish to use Automatic Updates, this is a necessary process. If not, you can safely disable the Automatic Updates service, which will prevent it from running. While it is possible to kill this process through the task manager, it is likely that it will immediately come back if automatic updates are enabled. The screenshot below illustrates how it should appear in the task manager:

Although in this screenshot, wuauclt.exe is running as SYSTEM, it can also run as the currently logged in user.

Dangers of wuauclt
As this is a process that runs on any Windows system with automatic updates enabled, it is common for virus writers and spyware vendors to disguise their malware as the genuine one.

Some malicious files will have the same name but will be stored somewhere other than in %SystemRoot%\System32. Other malware will use a name that appears similar to that of the legitimate one but with slight differences in spelling or with appended digits. The following malware is known to disguise itself as wuauclt.exe:
  • Backdoor.Clt (W32.Cult)
    • This is a backdoor trojan horse that gives an attacker full control over your system. If your wuauclt.exe is connecting to port 6667, it is likely that your system is infected with Backdoor.Clt.
There will typically be only one copy of this process running at a given time (although it is possible for there to be more). If multiple copies are running, one or more of the instances may be but are not necessarily malware.

Common problems
  • "Wuauclt.exe has encountered a problem and needs to close" when trying to update
    • Look for wuauclt.exe in %SystemRoot%\System32\dllcache and, under properties, check the version. Ensure that it matches the one in %SystemRoot%\System32.
    • If you have the KB927891 patch installed, try uninstalling it.
    • If the problem persists, perform a repair installation of Windows.
  • This process uses 100% CPU time
    • This can be caused by wuauclt.exe being stuck in an infinite loop trying to download a particular update. To fix it, disable automatic updates via the control panel and reboot the system. If wuauclt.exe is not running after a few minutes, you should be able to reenable automatic updates.

Automatic startup locations

001 Running Processes
002 Autorun registry entries local machine
004 All users startup startmenu
005 Current user startup startmenu
007 Roaming Start Menu\Programs\Startup
010 Installed services
033 Winlogon Userinit
065 Image File Execution Options (debugger)
135 Current User Runonce (+ subkeys)
167 HKLM Policies\Explorer\Run

Digital signatures found for this file

43 Microsoft Windows Component Publisher - Microsoft Timestamping Service
27 Microsoft Windows Publisher - VeriSign Time Stamping Services Signer
19 Microsoft Windows XP Publisher - VeriSign Time Stamping Services Signer
14 Microsoft Windows XP Publisher - VeriSign Time Stamping Service
12 Microsoft Windows - Microsoft Time-Stamp Service
10 Microsoft Windows Component Publisher - Microsoft Time-Stamp Service
7 Microsoft Windows 2000 Publisher - VeriSign Time Stamping Service
6 Microsoft Windows Component Publisher - VeriSign Time Stamping Services Signer
5 Microsoft Windows XP Publisher (Europe) - VeriSign Time Stamping Service
4 Microsoft Windows - Microsoft Timestamping Service
3 Microsoft Windows - VeriSign Time Stamping Services Signer

MD5 security rating in our database

253 files (Not yet rated and not signed)
6 files (Not yet rated and digitally signed)
196 files (Safe and digitally signed)
Some versions of this filename have not yet been checked for safety.
Warning: Some malware might rename itself to wuauclt.exe. Always make sure that your file is from a verified publisher.

User ratings for this file

File rating: Average rating of wuauclt.exe: by 455 files and users.

Application errors

Fix wuauclt.exe application error:  Run a FREE registry scan

User comments

Wauauclt eats too much processor!

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