Avastsvc high CPU on win7 since ~25aug2021

Avast Free Antivirus / Premium Security
1

It seems we are at least three persons to have the following problem :

  • avastsvc constantly uses 25% (on quad core CPUs) or 50% (on dual core CPUs) or more
  • trigger unknown
  • the machines on which this is happening are hosting windows 7 (specifically SP1?)
  • concerns 9 to 17 avast versions (please confirm?)

please report here if you are concerned too : give us you OS, avast version, symptoms

As for today, it seems to me this is triggered after a VPS update :

  • we are three win7 users experimenting the same thing around the world
  • after a factory reset from my whole system (2013 image) and an avast 9 offline install nothing happens with the CPU
  • then with an offline VPS update (2021.08.27 virus bases) the CPU goes up after x minutes (trigger unknown)

I do hope this problem is not a trick to push “old systems users” to upgrade.

TEMPORARY SOLUTION - STAY WITH AVAST 9 TO 17
Restart avastsvc with a file to make it use 0% CPU again (until it goes high up again…) :

  • create a text file anywhere
  • write inside the file EXACTLY this and save it :
    net stop “avast! Antivirus”
    net start “avast! Antivirus”
  • rename the file “restart.bat”
    → executing the file will stop then start the avast service

DEFINITIVE SOLUTION

  • update to avast 2021 : see official avast website - maybe a win7 update is necessary
  • update to avast 2019 or 2020 : to download google “site:filepuma.com avast 20[number]”
  • hey wait, avast 2019-2021 kills my weak old netbook…
2

Updated first post according to my new tests.

3

The same day that began the problems 25 August it was the announcement of the new version:
https://forum.avast.com/index.php?topic=299095.msg1649279#msg1649279

4

Many thanks for all the information you sent and all the tests you made. Iam very grateful!

5

I attach an image of the resource monitor to show the detail of the problem.

6

;)I was making some investigation and it could be possible that the problem appears when avast tries to make the rootkits analysis on startup in old versions.
turn off on troubleshooting-- rootkits analysis when start system
I will try I hope it could solve the problem. It is not an ideal solution but could be a temporary solution.

7

If my memory is correct the anti-rootkit scan starts 8 minutes after the startup.

8

I love you two, edialechu and DavidR for those informations !
I reinstalled Avast 9 without rootkit scan activated, and it works just fine for the moment.

Is it safe to do a VPS update + boot scan with sensibility at maximum + disable the rootkit scan if nothing is detected?

I guess a new rootkit would be detected by the File agent and/or the Web agent before it could infect the system?

9

I can’t say if it is safe to do a VPS update as it isn’t only virus definitions that get updated but also Engine updates. I also don’t know how the Engine and definitions update function in avast 9.

As for a new rootkit, well the reason for the anti-rootkit scan is rootkits by their nature can be well hidden and may not be found by conventional resident scanners.

10

It you try to activate rootkit scan it stucks or the service hangs on avast 9?

11

As I said (in another topic) it is unlikely that avast would be unlikely to spend time on old versions.

12

Hello guys, could you please reproduce the issue, collect and share with us the performance logs?
The description how to get those performance logs is available on this forum post:
https://forum.avast.com/index.php?topic=237567.0
Thank you.

13

hi thanks i created an account just to say i was trying hard to figure out why my cpu fan was working so hard constantly 100% cpu utilization on 1 core. thanks for creating this post making me feel that im not the only user that is facing this weird issue.

Windows 7 sp1 with avast 9.0.2021 and 10.4.2233

even after using avastclear and reinstall avast 9.0, upgraded to avast 10.0 didnt fix the issue.
disable rootkit scan fixed it thanks! most likely something in that 25AUG update triggered something else why have we been using it no issue for years?

couple of days ago i disabled rootkit scan, now i tried to enable rootkit scan again on my desktop, i cant seem to reproduce the issue!

i have a laptop my dad uses that has rootkit enabled all along and does not have cpu hog issue, not sure why?

14

Please update VPS to version 210903.8 . Let us know if the new version solved the problem.
Thank you.

15

Hey there.
First of all, thanks for having considered our problem on “old machines” and ancient Avast versions.

I’m using Avast 2014.9.0.2016 on Win7 SP1 with rootkit scan disabled for 3 days and it went ok.
I just updated to VPS version 210903.8 and rebooted : CPU goes up to 50% (= 1 core) after ~10 minutes like the initial problem i had but now it peaks at 99% from time to times. A full scan with everything maxed out (sensibility, whole file testing etc) still hangs at 0%.

16

Could you attach aswAr.log

17

Before i read your message, i launched two scans to test if they where functional :

  • scans with 210904.2 don’t hang at 0% (but yesterday they did with 210903.8)
  • … but the log you asked for has been replaced with the new ones so i can’t send yesterday’s log

Concerning the background protection, for this boot :

  • 210903.8 was installed at boot time
  • avastsvc CPU usage rose to 50% after ~10 minutes (rootkit scan it must be)
  • update to 210904.2 made before or after this peek?
  • i stopped/started the avastsvc via a net command
  • 8 minutes later, with 210904.2 installed, avastsvc CPU usage is normal
18

Three boots later, Avast 2014.9.0.2016 on Win7 SP1 with rootkit scan enabled, everything seems fine.

I guess the issue’s been corrected for me.

Thanks a lot to edialchu for having alerted on the rootkit scan, to DavidR for the 8 minutes root kit scan delay, and to jaroslav.nix + gmer + the avast team for having considered our troubles !

19

You’re welcome.

Note, gmer is on the Avast Team, specialist/designer on the anti-root kit module

20

You are welcome avast_user321654.Thanks to you for all the information and help you sent!