What happened to Avast! - time to complete a full virus scan increased by 113%

I always do a full scan of my computer Fridays and since the 17’th of Feb the time to complete the full scan has increased by 113% from about 53 minutes to 1 hour and 53 minutes.

The amount of folders, files and data is pretty much the same so whatever is causing this seems to be in the latest version(s) of Avast!

Hope there’s a solution to this, seen others reporting the same thing.

Strange… was there anything detected during the scan?
Did you change any settings of the full scan (not necessarily now, possibly some time ago), or is it on default?
What version of Avast do you have? Did you possibly update to the new version in the week before Feb 17?

Where are others reporting the same thing?
Thanks.

The first time I noticed this on the 17’th of Feb a number of issues were reported of which I’m certain they were all false positives. However I didn’t use the files affected anymore so I decided to delete them just to make sure. Here’s a screenshot of that scan but a bit hard to see due to the bad 4K scaling in Avast.

https://dl.dropboxusercontent.com/u/94801887/Avast%20bad%204K%20scaling.JPG

Today I had an issue reported as well and not sure if it was a false positive or not. The file triggering the alert was a file in my recycle bin called $ROM093N.adi where the threat reported was Win32:Hupigon-ONX [Trj]. I decided to move the file to the chest thinking I might want to investigate it further and it looked like Avast! was able to successfully carry out the action I asked for but when I later checked my virus chest it was empty?!

I also find the new GUI to be a bit confusing not really letting me know when an action has been completed…in this case moving the suspected file to the virus chest. Instead I had to manually press the ‘Back’ button and I could only assume the action had completed successfully.

I then decided to restart my computer and do another full virus scan and this second scan came out blank with no reported issues and it took just as long as the first one just under 2 hours vs the normal just under 1 hour.

I’m pretty sure this started with the latest version of Avast and the new GUI. Never saw this issue with the previous version(s) of Avast!

Here’s another guy reporting very slow scans recently → https://forum.avast.com/index.php?topic=197802.0

Sorry, forget to comment on settings used for the full scan. Nothing changed in there as far as I can remember. What I did try was to enable all settings found under the performance section on the settings page and I also changed the prio to high but all to no avail I’m afraid.

Yes it is true for me also. Scan time did increase a bit. A lot of time is wasted showing 'initializing".

Thanks for your input and if in your case the scan time only increased a bit I guess you should consider yourself lucky since in my case it increased by more than 100% :wink:

So will full scans take this long now or did you identify any issues that could have caused the increased scanning time in latest version(s) of Avast?

Scan times are taking a bit longer.
That said, scan times will significantly decrease as you populate the persistent cache.
Just be sure you are using the populate the persistent cache in your scan settings.

It’s set that way by default. :slight_smile:

I don’t believe it is, some considerable time this ‘Speed up scanning by using the persistent cache’ was checked by default but the ‘‘Store data about scanned files in the persistent cache’’ was unchecked. I had to check this item some time ago (for the Full and Quick scans, the Smart Scan doesn’t appear to have any settings icon. I always check it is enabled after a program update.

I just checked the various scan settings and some of them still didn’t have it enabled by default. Now that was the USB/DVD scan, the Folder scan and the boot-time scan. There might well be a reason for that, but I can’t see why some would be checked and others not.

I don’t know what settings you have your screen shot. I referred to this:

http://screencast-o-matic.com/screenshots/u/Lh/1488555827518-7845.png

Bob your image is for the file system shield and not on-demand scans which is essentially what the OP is saying is taking too long or much longer.

I always do a full scan of my computer Fridays and since the 17'th of Feb the time to complete the full scan has increased by 113% from about 53 minutes to 1 hour and 53 minutes.

My image is from the various on-demand Scan settings in the AvastUI > Protection > Antivirus > Other scans.

I stand corrected. Probably because for me the on demand scanning isn’t really needed if you have a clean system.

I too rarely use it, mainly in relation to helping in the forums :wink:

Thanks for your input guys!

I’ve been using Avast for a very long time so I’m well aware of the persistent cache settings and I made sure the one populating the cache was checked at least once since I started having this issue but didn’t notice any difference I’m afraid.

Maybe a bit over the top running manual scans for most people when you have real-time scan active but I’m extremely careful with my system since it’s a very complex one taking weeks to setup so I don’t take any chances.

Also I have areas of my system excluded from the real-time scanning for performance reasons making it even more important to have these areas scanned manually every now and then in my case once a week.

Clearly something changed in the latest version(s) of Avast as already mentioned because I’ve been running the exact same scanning method for years using Avast and with pretty much the same kind and amount of data on my computer and now all of a sudden it takes more than the double amount of time to complete.

I hope we’ll see this addressed swiftly. If not maybe it’s time to start looking for alternatives.

If this was a clean install rather than an update from the UI or an install over the top of your existing avast version, then it may be possible that the persistent cache was cleared.

If that were the case it could take a few scans to actually populate the persistent cache.

Also as Igor was getting at, if there were detections during the scan, that would have a profound effect on the scan duration. When a detection is made avast goes into a paranoid (for want of a better word) sensitivity and this would prolong the scan.

I had previously done some test scans and watching the scan % progress, when a detection is made you see the % scanned drop considerably. I have seen it drop from around 69% back down to 24%.

Guess I could run a couple of extra scans with the ‘Store data about scanned files in the persistent cache’ option checked to see if that will eventually improve the performance. How do you recommend I set the ‘Speed up scanning by using the persistent cache’ option while doing this…checked or unchecked?

As for the ‘Speed up scanning by reading files in the order they are stored on disk’ I have that option checked. Not sure though how much benefit I’ll have from that option using a very fast SSD disk.

I’ve also tried changing Scan priority to ‘High’ but haven’t seen any difference doing so.

Really strange all this because as I’ve already said I’ve been using Avast for years and years and never as far as I can recall have I seen this problem before how the time to perform a full manual scan has doubled.

“it’s a very complex one taking weeks to setup so I don’t take any chances.”
Regular image backups would cut that time and offer the ultimate protection. :slight_smile:
Remember that your AV doesn’t protect you against hardware failure.

@ WebMaximus
Since that is a default option, I would leave the ‘Speed up scanning by using the persistent cache’ option checked (enabled).

I have systems with HDD and SDD hard drives as the primary drive, but the way I see it with an SDD they are less prone to the hassles of location as in an HDD drive. But I can’t see that hurting if it is enabled, after all SDD soft/firmware would be placing files to prevent/balance writes to the SDD. I also don’t know how much impact TRIM would have in relation to that setting.

But this XP Pro system has HDD as the primary so I would probably get greater benefit from that option.

If you are running these scans at a time when you are using the system, it is going to be slightly hampered even if set to High priority. After all I thought that was the point of scheduling scans. That said some are reporting issues with scheduled scans starting as per the schedule.

I certainly feel a robust backup and recover strategy would be a better way to go.

Let me assure you I’m well aware of that and I’m already using software to perform complete image backups and those image backups in turn are also backed up on a separate disk in another physical location from where my computer is but…

…imagine if a virus found its way into my system and I didn’t know about it until I already had it in both my image backups as well as on my image backups backup disk…I do what I can to avoid that.

I fully agree a robust DR strategy is mostly your safest and most convenient option but IMO that doesn’t make a likewise robust AV strategy obsolete.

I do appreciate your input guys but what I really want to know is what I asked already in the subject line when I created my first post - what happened to Avast all of a sudden taking the double amount of time to complete a full manual scan.