AvastUI.exe using 90%+ of CPU and slowing machine to a crawl

Avast Free Antivirus / Premium Security
1

Having just spent the past week or so building a new machine from parts, I started to load the software onto it. I started with Windows XP (I know, but there’s a reason why I want it to run XP), followed by all of the other stuff I wanted on it.

Having ditched AVG in favour of Avast when they introduced that stupid and highly intrusive Zen thing, Avast Free was the first thing to go on after Windows. Everything seemed fine until a couple of days ago when the machine suddenly slowed to a crawl. Checking Task Manager, I saw that the CPU was maxed out at 100%, with AvastUI.exe being the main culprit at 99%.

Even letting the machine sit there idle for over an hour, it would still be maxed out at 100%, with AvastUI.exe using 90%+ (usually pegged at 99% for most of the time).

Checking things online, I saw that I’m not the only one to have this issue, so I started to work through the various things people suggest as a solution, but things like turning all of the shields off didn’t help.

I tried repairing the installation, but that didn’t help either. So I went into safe mode and used the utility to completely remove all traces of Avast. Rebooting without any AV loaded at all, the machine was fine, and sat there happily with CPU use at 0% while idling.

I then reinstalled Avast Free from a fresh download of the installer and, guess what? Yes, that’s right, it went back to AvastUI.exe using 99% all of the time.

I’ve checked, and I am able to use Process Explorer to create dump files.

The version of Avast Free is 18.5.2342 (build 18.5.3931.0) and, while I do have other AV/anti-malware programs on the machine, such as Malwarebytes Anti-malware (version 3.5.1.2522), as far as I’m aware none of them are set to load at boot-up and only run when called manually by clicking on them. I certainly can’t see any of them running in Task Manager or Process Explorer.

The machine is a P4 2.8GHz with 2GB RAM and a 2TB SATA HDD, running a fully-updated fresh install of XP Pro SP3 uploaded from an official genuine CD (SP1 on the disk, SP2 and SP3 from my own downloads from the Microsoft website a couple of years ago when needed for another machine).

This issue has definitely got me puzzled, as I use Avast Free on other machines with similar software (all Windows XP Pro SP3), and none of them seem to have this issue - including the one I’m using to write this now. So any help people can give in solving it will be greatly appreciated.

2

Regarding Avast & Malwarebytes, see: https://forums.malwarebytes.com/topic/200324-exclusions-for-avast-users/

3

Thanks for helping!

OK, tried that and rebooted, but no effect as CPU use still stuck at 100%, with AvastUI.exe still using 99%.

As I said in my original post, MBAM and the other programs are not set to run on system start-up, only when called manually, so I can’t imagine it being some sort of resource clash with Avast. And, as I also pointed out in my OP, the machine I’m using to write this now has similar software on it, including both Avast and MBAM, and it doesn’t have the same issue (CPU usage at about 30%, with AvastUI.exe using about 3%).

4

I noticed that my new AvastUI.exe was using 50% CPU after booting Windows XP, but when I started other programs it would respectfully drop down to 0%. After a few days this behavior has ceased, and it now goes to 0% a few minutes after booting. My guess is that it was doing some sort of initial scan after being installed, and that is now complete. I understand that your problem is far worse, but you could try just leaving it alone for several hours and see if it stops using the CPU.

5

Well, I’ve already tried leaving it alone for four or five hours, but that doesn’t seem to do any good, and AvastUI.exe is still using 99% even after all that time, so I don’t think that’s it.

6

Hi lather30,

You could try uninstalling Malwarebytes Free and reboot.

They also have a full uninstall tool here: hxxps://support.malwarebytes.com/docs/DOC-1112

[EDIT:] New site, old link bad: https://www.bleepingcomputer.com/download/malwarebytes-anti-malware-cleanup-tool/

Reboot.

7

That link doesn’t work - it just takes me to a dead-end at a login page with no signup option. So I had to do a bit of searching around on Google to find the correct download link.

Malwarebytes Free uninstalled using the cleanup utility, system rebooted and left for things to settle down, CPU still pegged at 100% with AvastUI.exe still using 99%.

So I guess that confirms it wasn’t Malwarebytes Free that was causing the issue.

8

That’s odd. Tested site before I posted and got the same executable provided above at bleepingcomputer.com. Something changed.

Sorry about that.

9

Follow instructions: https://forum.avast.com/index.php?topic=218231.msg1458060#msg1458060

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Dump file created and uploaded using the filename given in the message quoted (avast_ui_exe_cpu_peak.zip) - no password as created the zip file before reading the ftp instructions at https://support.avast.com/en-gb/article/FTP-file-upload (also the Windows “send to zip folder” menu didn’t give me that option).

11

OK, I’ll forward it to kwiq.

12

Hi lather30,
I went through all threads and there was only one active thread which belongs to datascan component.
Can you try to disable this feature and let us know if it helped ! For example via ini file
C:\ProgramData\AVAST Software\Avast\avast5.ini in [DataScan] section there is option Enable=1 please change it to Enable=0

Thank you

13

Note for lather30, before trying this you will (may if nothing has changed) need to disable the Avast Self-Defence Module in the AvastUI > Settings > Troubleshooting.

For the actual edit you should also use notepad, no other text editor (even with the Avast Self-Defence Module disabled).

14

OK, tried that.

Self-protection disabled.
Setting changed in Notepad & file saved.
System rebooted and left idle for 1 hour to settle down.
CPU still at 100%, with AvastUI.exe still at 99%.

15

OK, we will have to wait for Avast Team member kwiq to get back to your topic.

16

Hi lather30,
in win7 and above I would suggest xperf logs as this is the best tool for CPU issues but XP doesnt support it :frowning: .

In xp i know only about procdump from : https://docs.microsoft.com/en-us/sysinternals/downloads/procdump
Disable self defense
Please download this tool and create a set of dumps with command - cmd as admin : procdump -c 50 -s 5 -n 10 AvastUI.exe
zip them and upload them to avast ftp.

Thank you

17

OK, I downloaded, installed and ran ProcDump using the listed commands. For some reason, it was only able to get 9 dumps, as the 10th failed to write due to an error message about a device attached to the computer having failed or stopped working - although I can’t see any evidence of a problem.

Zip file of the 9 dumps it did get uploaded to FTP with the filename AvastUI.exe_180807_152731.zip.

18

Any progress on solving this? It’s now 11 days since I uploaded the requested dumps, and I’ve not heard anything more about it. Is it solvable, or have I got to start looking around for a different AV program to use? Hoping for an answer one way or the other soon, as I can’t afford to have the computer sat around idle for much longer.

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Reported let’s see if that helps.

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Apparently not, as I’m still awaiting a response - now 2 weeks since the dumps were uploaded.

On the off-chance that it may help solve the problem, I updated to the latest version (18.6.2349), but the problem still remains the same, with AvastUI.exe using 95% to 99% of the CPU all of the time.