how thorough a scan do I need?

[garymonz]

Just ran a whole system scan, and it took at least four hours to go through the whole disk!!Seems way too long. I had the setting on high. Is that the problem?
Also, is there a way I can get a scan on a periodic basis, or is it doing it every time I log in? I notice the ball icon spinning when I do.

[galooma]

Hi and welcome ,
That seems a bit long to me. Normally scanning around 30 gb of HD on extreme settings and within archives takes around 80-90 minutes for me at most.
I am presuming you havent got any enormous 200 gb drive loaded up with game files and movies  and a reasonable processor then something strange is going on.
 Was this the only program you had running?
What OS/platform are you working with?
 Incidently I personally only run this deep a scan if something strange is happening. Otherwise normal settings are fine. Same goes for your providers.
 As for the frequency , thats something you have to decide and it should be based on how cautiously/recklessly you surf,and wether your system is handling a lot of traffic from multiple users, or just one user who goes to the same sites regularly and rarely has any infections. In the case of the latter you might find once per month is fine with maybe a trojan scanner in between.

To scedule scans is only available on Pro version but it is possible within windows scheduler see : http://forum.avast.com/index.php?board=2;action=display;threadid=3796
or by dos cmd prompt
http://forum.avast.com/index.php?topic=17282.msg148375#msg148375
good luck

[Lisandro]

Just ran a whole system scan, and it took at least four hours to go through the whole disk!!Seems way too long. I had the setting on high. Is that the problem?

Setting to High will scan every single file that you read, open, write, etc.
Maybe you can set the sensitivity to Normal and use a better balance of resources and protection.

Also, is there a way I can get a scan on a periodic basis, or is it doing it every time I log in? I notice the ball icon spinning when I do.

On-demmand scanning can only be scheduled into Professional version.
The ball sppining is due to on-access scanning...

[Umath]

How about putting large data files to a special folder/disk/partition and letting Avast ignore it?

My system/application partition is about 3-4 GB while other few hundreds are dedicated to data files.  Normally, I let Avast scan only the system/application partition, which takes less than 20 minutes even with the through scan.

[DavidR]

I exclude my hard disk images from being scanned as avast effectively can't do anything with a disk image even if it were able to find something in it.

The only other thing that could possibly reach these sizes huge video files or the pagefile.sys file which I have also excluded.

[Lisandro]

I exclude my hard disk images from being scanned as avast effectively can't do anything with a disk image even if it were able to find something in it.

I do exactly the same