Author Topic: How to fix Avast Antivirus High CPU Usage  (Read 36307 times)

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How to fix Avast Antivirus High CPU Usage
« on: March 02, 2016, 12:36:39 PM »
So a while back, I noticed that my CPU performance was decreased. I tested using wPRIME running a 32M benchmark. Without an Antivirus installed, I would get a score of 4.9 seconds, with Avast Antivirus Pro installed, I would get 7.5 seconds (the lower the score the better).

I then posted this thread on the avast support forums:

Avast Antivirus Pro affecting CPU Performance

No help was offered and I was just told that any Antivirus would cause a small hit on the CPU performance.

I then installed NOD32 and Kaspersky Antivirus (separately off-course) and benchmarked again but I would get 5 seconds in wPRIME so that was all good and the issue seemed to only be there when Avast Antivirus was installed.

This surprised me because according to the latest AV-Comparatives Performance tests, it shows that Avast Antivirus is one of the lightest solutions out there.

I then submitted a support ticker to Avast which as usual, took almost 2 weeks to be answered.

They suggested to change a few things which I did and now my CPU performance is back to normal, I am getting 5.3 seconds in wPRIME so a 0.3 seconds performance hit is fine.

Here are the suggestions from avast! Support to remedy this problem whilst not really affecting your security:

Let's try to make Avast running faster by removing some additional  features and adjusting few settings. Please follow these steps to do so:

First please repair and update your Avast installation:
Click on Start > Settings > System > Apps & features > Avast installation > Click on "Uninstall" > REPAIR > Continue.
After the repair, please make sure that you have the most recent version of Avast - 2016.11.1.2253.
To do that, please open Avast and go to > SETTINGS > Update > Program > Update and update your Virus definitions as well.
Restart your computer.

After that please disable few additional Avast features:
Go to Start > Control Panel > Uninstall a program (Programs and Features, Add or Remove Programs)
Select Avast and click on Uninstall/Change.
In the Avast window that appears click on "Modify" > Continue > now under "Tools" uncheck the following:
- Browser protection
- Avast SecureLine
- Cleanup
- Passwords
- Secure Virtual Machines (if present)
- Secure DNS

After that click "Continue" and after changing of the product will finish, restart your computer.

Finally please adjust Avast Web Shields settings as follows:
Open Avast and go to > Settings (gear icon) > Active Protection > Web shield - Customize > Main settings.
There please uncheck/deselect following settings:
- Use intelligent stream scanning
- Enable HTTPS scanning
- Script scanning

Restart your computer again.

This will only remove few new features, all important Avast features will remain unaffected and the protection level of your machine will remain the same.

Offline Eddy

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Re: How to fix Avast Antivirus High CPU Usage
« Reply #1 on: March 02, 2016, 12:52:30 PM »
There is no need to start a new thread about the same.
Stay in your original thread.

Offline igor

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Re: How to fix Avast Antivirus High CPU Usage
« Reply #2 on: March 02, 2016, 01:03:37 PM »
Some of those suggestions (such as disabling HTTPS scanning) are definitely dangerous and limit Avast protection in a significant way (i.e. not a good idea to do that).
Uninstalling some of the features (Passwords, Cleanup, SecureLine) should be OK if you are not using them, but based on how they work, I don't believe they can affect the performance of the machine in any way.

In my opinion, the slowdown you experienced was caused by some preparation (such as Secure Virtual Machines building its snapshot) and would go away after some time.


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Re: How to fix Avast Antivirus High CPU Usage
« Reply #3 on: March 02, 2016, 01:10:27 PM »
As support said, this will not lower your security because once the file is downloaded, if it was malicious, the active file shield will block it anyway so no harm done.

I personally dislike programs which do HTTP scanning, like I have a NOD32 license for 10 users valid until 2020 which is collecting dust as it slows down everything for me, internet browsing, downloads, etc. wish I could sell it

Offline igor

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Re: How to fix Avast Antivirus High CPU Usage
« Reply #4 on: March 02, 2016, 02:55:53 PM »
I'm afraid the support is wrong in this case.
You are assuming that the malicious code always has to be written to disk; if it is, then yes, the File System Shield (probably, because it has lower sensitivity than Web Shield) detects it. However, some malicious content (let's say in HTML or script form) may be interpreted/run by the browser without (or before) being written to disk.