Summary: Many people are experiencing high CPU usage, often 100%, in svchost. Svchost is not a virus, but many people think it acts like one.
After I log in, my system slows to a crawl. Looking at task manager I see that my computer is experiencing high CPU usage. Looking more closely I see that something called "svchost" is taking 100% of my CPU time. If I kill the process suddenly other things stop working. Is svchost a virus? How do I fix this svchost problem?
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Important: please see the update near the end of this article.
That's actually a composite question based on several reports I've been getting recently.
Svchost is not a virus. In fact it's a required system component. You'll often find several copies of svchost running.
Svchost, or more correctly "Service Host", is a program that is designed to run other programs and "hosts" many of the system services in Windows XP. Several copies of Svchost run more than one service, which is why when you kill an instance of svchost several things on your machine might stop working.
So why is one of the Svchosts taking all your CPU?
And what can you do about it?
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From what I've heard and have been able to tell, this is nothing more than a bug. A serious and annoying bug, but a bug nonetheless.
The bug appears to be related to the Windows Update service - the service that you're supposed to keep running at all times so that updates will be automatically downloaded to your machine.
A quick way to tell if this is happening to you is to download Process Explorer and right click on the svchost instance that's taking 100% of your CPU and then click on the Services tab:
You can see that this copy of svchost on my machine is running not only The Windows Update service, but is actually running 29 services all totaled. So if you were to kill this instance of svchost you'd be killing all of those services and many features and functionality of your system would fail.
One Temporary Solution
One approach to this problem is to stop and then disable the Windows Automatic Update service. If you have it open in Process Explorer, as shown above, with Automatic Updates selected in the list, then just click the Stop button. If your CPU usage then drops to more normal levels, you've identified the problem.
To prevent the Automatic Update service from starting again, right click on My Computer and click on Manage. Expand Services and Applications, and then underneath that click on Services. In the resulting list on the right, locate Automatic Updates:
Right click on Automatic Updates and click on Properties. Change the Startup type to Disabled:
(You can also click Stop here if you didn't stop the service earlier.)
Click OK and Automatic Update service should be disabled.
IMPORTANT: since you won't be getting updates automatically, you should now plan on visiting the Windows Update web site periodically to make sure you keep your Windows up to date. As we'll see shortly, this will also become important to resolve this problem "for real".
Another Temporary Solution
Folks commenting on a previous svchost article have reported success by removing and reinstalling Windows Update.
Specifically a series of commands detailed at amset.info labeled Remove and Reinstall of Automatic Updates seems to resolve the issue for many people.
I haven't tried this solution since I've not experienced the problem, but as I said, several folks are reporting good results.
A Permanent Solution?
There isn't a permanent solution. Not yet anyway.
There are rumors that Microsoft actually has a fix, but that you need to call up and ask for it rather than getting it through normal channels. I'm not convinced that this fix is actually for this specific problem that so many people are experiencing.
There are also rumors that Microsoft will be making the actual fix available in a future automatic update. Ironic, since it's automatic update that you may have turned off in order to work around the problem. That's why I recommend making certain you regularly visit Windows Update and take the latest fixes to keep your system up to date, not only for this issue but for any other issues that may crop up over time.
Also, remember, once the problem is fixed, be sure to re-enable the Automatic Updates feature. It remains an important part of keeping your system safe and up to date.
Update!
23-May-2007
I woke to find this automatic update waiting to be installed on my machine this morning:
This is the update that's been frequently referenced as a resolution for this problem.
It's possible, perhaps even likely, that this issue will now get put to bed. It's your choice at this point: you should be able to visit Windows Update to take the fix, enabling Automatic Updates again should get the fix downloaded, or you can visit the knowledgebase article to get the fix.
Article C3020 - May 9, 2007
Hi Leo, I was having a problem but really did not noticed untill it got serious. I was working on my PC and if I had to open an Internet connection when Tried to Close it or work on it, it freezed, then I used the task manager to terminate this process, the screen looses all the icons at desktop for a few seconds and then they came back, also a windows message: "Windows can not find C:Documents", I look for help on the net and foud a stupid one: "If the system asks you for C:Documents, so create a folder in C, called Documents", what a solution!
I keept my search for help and for this SVCHOST theme, that´s how I got in your helping site.
Now when I left my pc all nite downloading and of course with internet connection workin, in the morning I find an Explorer page with message: Too many connection and had to close" (or somethig like that), so I close and when I try to open IE again it says if I want to recovery the previous pages that did not close properly, so I say OK, and inmediatelly open 10 pages with porno images of diffenet named sites.
I tryed the: Ad Aware, and the Super anti Spyware, they found some issues and supposed to clean them, but the problem is still running on my PC. I have Avast updated and Avira.
I need help 'cause when I am workin the PC Freezes and if I am workin on any other program, such as Photoshop, Vegas, Audition, or else, if it freezes the only solution is to terminate processes and I might loose hours of work.
Hope you understand my poor english but it's not my natural languaje, mine is spanish.
THX a lot for all you can do for helping me.
Alexius
Posted by: Alexius at February 21, 2010 4:00 AMHoly crap, this really helped! I assumed since I'm still running on the Windows 7 trial, this is why I'm getting high CPU usage. Since it's a trial, I can't get any windows updates, but now that I turned it off, my computer is running like a beast. Wow, seriously, I am so happy for this information.
Posted by: Albert at March 8, 2010 11:39 PMI´ve heard that there is no ONE solution to this problem, but I´ve had it for several weeks and basically read everything about solutions! But, there IS a God! And it´s name is UNIBLUE!!
Posted by: Egill (from Iceland) at March 10, 2010 10:22 AMAnd it´s located right on the Windows 7 microsoft site :) !! Fixed ALL my problems . . . and know I´ve even boughtDriver Scanner as well ! All Hail to Uniblue :) !!
No!! I was wrong, like everybody else :( !!
Posted by: Egill (from Iceland) at March 10, 2010 3:03 PMBut I´ll keep on trying :) !!
None of this worked for me....I tried just about everything I came across for hours last night (100% CPU under svchost.exe). The last thing I tried was running the free version of "Malwarebytes' Anti-Malware" (I had tried other anti-virus/malware that didn't find anything up to this point). It found quite a lot the first time through and I ran it a second time for good measure. Everything is back to normal this morning...maybe this will help if none of the other recommendations are working for some poor soul out there!
Posted by: Ron at March 13, 2010 9:12 AM