Monday, October 8, 2018

windows 10 - High CPU usage unless task manager opened, but no rootkit detected



I am using Windows 10 (v1903). Whenever I open Task Manager, I see that CPU usage is at 100% -- but then it plummets to ordinary numbers (typically below 20%). This change happens so quickly that I cannot see what task is using so much of the CPU.



The problem seems like the one described in Windows 10 high CPU usage unless task manager is opened. But I have tried the advice given in the answers to that post, and the problem persists. Which makes me wonder whether it is a problem at all. Specifically:




  • The following software has turned up no serious problems: MalwareBytes (run from my normal boot drive and again from Hiren's BootCD), ESET online scanner (run from Hiren's BootCD), Norton Endpoint Protection, and McAfee's rootkit detector.


  • When I use Process Explorer to gauge CPU usage, I don't see a problem. Most of the CPU usage in Process Explorer is attributed to "System Idle Process."


  • A Windows Defender offline scan just runs, stops for a reason I can't discern, and reboots the computer. It doesn't leave an entry in the "Protection history" section of the Windows Security app. It does leave a log file saying that "On demand scan closed without completion."



  • GMER rootkit detector crashes with a BSOD, even when run in safe mode and when Windows' built-in virus and threat detection are disabled.




Is there a way to identify the process using so much of my CPU? Or should I simply conclude that the Task Manager results are more suggestive of a nuisance than a real problem?


Answer



The behavior you notice is normal for machines using V1903. I see it on all my own and client machines. It is just Task Manager normalizing and nothing to worry about if CPU is normal after 5 seconds of starting Task Manager



For Windows Defender, look in Start, Settings, Updates and Security, Security and see if WD is putting anything into Quarantine.



Run DISM and SFC to do basic checkups. Admin Command Prompt:

dism.exe /online /cleanup-image /restorehealth follow by SFC /SCANNOW



Restart when done


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