Member Avatar for sepand

Just out of the blue today, my fan started working consistently and things got really slow, until I could no longer access task manager or the start button. I restarted the computer, only to come back to windows and find the same problem. The 2nd reboot, I managed to get the task manager up as soon as windows started, and noticed that svchost.exe was reading at 99%, and eating all my cpu usage. I closed it and came to post this problem on the website. I don't know if it's related but when I opened firefox it looked different at first (kinda more primitive??), and asked me if I want to have firefox as my default browser (I had done that ages ago).

Any ideas why? I'm going to run some scans now, see what comes up...

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svchost.exe itself is just a host for Windows services — seeing it at 90–100% CPU usually means one of the services inside that host is stuck or looping, not that “svchost” is a virus. Quick kills can restore responsiveness but won’t identify the cause. The posts above show this can be caused by either a misbehaving service, update components, or (less commonly) malware; those are the angles to check in order.

First, identify the offending service. Find the busy svchost instance (Task Manager → Details/Processes, note the PID). From an elevated command prompt run:

tasklist /svc /FI "IMAGENAME eq svchost.exe"

or use Process Explorer (Sysinternals) — double‑click the svchost process, check the Services tab to see which named services it hosts, and the Threads tab to find which thread is consuming CPU (stack trace helps pinpoint the DLL or service function).

Once you know the service name, test-stop it safely:

sc queryex <ServiceName>
net stop <ServiceName>

If Windows Update components look involved (as noted by ), reset them cleanly from an elevated prompt:

net stop wuauserv
net stop bits
net stop cryptsvc
ren C:\Windows\SoftwareDistribution SoftwareDistribution.old
ren C:\Windows\System32\catroot2 catroot2.old
net start cryptsvc
net start bits
net start wuauserv

Run Windows Update again after restarting.

If malware is suspected, boot to Safe Mode (or use an offline rescue ISO), run multiple up‑to‑date scanners, and collect logs before making major changes. Follow ’s advice to scan, but try targeted identification first so you don’t reinstall unnecessarily — reinstalling (as suggested) is a last resort. Always back up personal data and exported settings before major repairs. If asking for help, include the busy svchost PID and the output of tasklist /svc so responders can see which service was hosting the CPU usage.

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Member Avatar for sepand

Alright, things NOT looking good. Windows Defender automatically found the following:
Spyware:Win32/C2lop.B (Alert Level: Severe!!!)
Program: Win32/StartNowHyperbar (alert level:high)
Adware:Win32/NewDotNet (High)
Trying to remove now.

Member Avatar for Sturm

reinstall.

Member Avatar for joshSCH

did you have windows defender delete those? If I were you, I would download more dependable software such as ad-aware se personal and avast anti-virus. Run some scans from those programs, and your troubles should be over =)

Member Avatar for sepand

I have ad-aware SE, AVG (formerly known as Ewido), Norton anti-v, SPybot, and a host of other programs. It wasn't a virus, although funny enough my Windows Defender did start picking up viruses on my HD (one of them was the uninstall file for WAREZ). The problem was with windows update. As soon as I changed to having only windows update instead of windows and office updates, everything was fine :D

Member Avatar for joshSCH

lol.. seriously? Well, okay then..

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