In order to speed up my system, I often keep certain folders (like my download, archive–with already scanned files, and certain temproary folders) on my folder exclusion lists, to prevent Avast and other software from continuously intercepting and/or redundantly re-scanning files that are in a partial state or already scanned. Sometimes, I’ll even turn Avast completely off when downloading several software tools in batch mode so I can quickly download everything at once and go back to normal operation without sitting around twiddling my thumbs waiting for everything…
However, once everything is done… I’ve noticed that if I highlight the freshly downloaded files and tell Avast to scan the files, it happily opens the scanning popup window, then promptly reports no threats found–And a total of 0 bytes/files scanned! What I discovered was that if I turn the virus scan engines off and/or add the folders to the exclusion list, it won’t ever scan them, even if I specifically tell it to. Instead, I have to move the files to a different folder (or remove the folder exclusion), make sure all virus scan engines are running, and then scan. (And even then, sometimes it doesn’t seem to want to scan the files until I reboot!)
What would be nice is that if I specifically select a number of files and folders and tell Avast to scan them, it’ll “do or die” scan them, overriding file/folder exclusions and/or scanning engine status; Temporarily enabling them for the one-time scan.
This would also be nice because I do periodically re-scan my archive folders (about 300 gigabytes of files!) once every month or two when new virus signatures are in place, to catch anything older signatures may have missed. (Perhaps even an option to add last scan data and signature version to the files, either appending data to the files default data stream, in an alternate data stream on NTFS, or a supplementary file… Maybe even alongside MD5 or SHA256 digests to verify the files are unchanged since last scan… I already do this manually, but it’s a lot of work and moving files back and forth…)
avast already has that feature it’s called the “persistent cache”. Once scanned a file won’t be scanned again unless it has been accessed.
As far as scanning archive files, what’s the purpose in that? Archive files are by nature inert and don’t need to be scanned. Once “any” file is
accessed the file shield will then scan the file using the latest and most up-to date virus definitions. With v2014 avast implements “continuous
streaming updates”. Continuous streaming updates are released approximately every 3.5 to 4 minutes.
I’ll have a look at the persistent cache feature, and see if it helps. For the most part, yes, the archived folders are no scanned as often because most scanning is done “on demand”, but none-the-less, I have noticed that when scanning is turned on and running, especially without excuding my archives, my system memory and CPU loads takes a small noce dive–About 15-25%. Not a lot, but enough that when I’m trying to get things done, it slows me down. So I turn it all off. Part of the problem may well be that I’m not aware of or using any persistent cache, and any time Windows Explorer had the folder open, it’s reading/accessing the files for icons and other metadata, causing the demand scanner to re-scan the files… Defeating the purpose of only scanning on demand/as needed.
Of course, that still won’t solve the idea that if I specifically tell Avast to scan a file, it should override any other settings and do a complete scan of the file, regardless.
If you place a specific folder into the Global exclusions, then yes - they won’t be scanned at all. If you placed them e.g. only to the list of FileSystem Shield exclusions, then it wouldn’t apply for on-demand scans.
But honestly, the whole scenario isn’t really good… it’s not the same to scan files manually, compared to real shield detections. The shields have additional context (e.g. where the file is being downloaded from) they can use when deciding whether a file is good or not; on-demand scans don’t have that information - so some things may go undetected.