1a. Are ‘Quarantine,’ ‘Virus Vault,’ and ‘Virus Chest’ the same concept?
Answer:
b. Is the difference between ‘Web Shield’ and ‘Quarantine’ that WS displays a threat pop-up and aborts the website connection (so nothing is saved to the computer and nothing would be found in Quarantine) whereas Quarantine is when Avast detects a threat in real-time (or through a scan) and places the infected file there?
1a. they are essentially the same (slightly different terminology), a location where malware is placed so they can cause no harm.
1.b the web shield scans web content, intercepts and stops it getting to your system (if found to be harmful), so there is no need for it to be quarantined/sent to the virus chest.
The file system shield scans active files on your system, on-demand scans as the name implies are run according to your settings. For the most part they would be scanning dormant files (or they would be scanned by the file system shield if active.
I understand that Web Shield scans web content, intercepts it, and stops it getting to the computer (if found to be harmful). As a result, there is no need for it to be quarantined/sent to the virus chest.
*Under what circumstances would malware be placed in ‘Quarantine’ or am I getting mixed up between web content (WS) and a malware file (Quarantine)?
The web shield doesn’t send anything to Quarantine.
It monitors your browser traffic, blocks harmful content or connections to websites you would have otherwise have connected to. It intercepts web traffic that would otherwise be downloaded, scans it, if fine allows it to be downloaded or displayed in your browser.
Files that get sent to quarantine are for the most part detected by the file system shield, something on your system or something you are copying to your system could be infected.
The File Shield scans, all New, Modified or Executed files before they are allowed to be saved (new file) or modified or run. If they are found to be infected then they will be sent to the Quarantine/Virus Chest. Typically this is for files that are active (can be run, e.g. executable files) or files that can run. Also if you have a zip (compressed) and you try to open/run that files that are extracted would be scanned before being allowed to be saved to your system.
There really is nothing to worry about the circumstances of the why and wherefores they would be quarantined as it isn’t something that happens without your knowledge. Avast Would first Alert you to a malware problem and display a screen with the information, for most instances the default action would be to send them to quarantine.
The above is pretty much the default action, unless you change the Core Shield settings and I wouldn’t recommend that, a more experienced user may elect to be notified (ASK) and they make the decision on the action to be taken.
Not quite - modified or executed files that are ‘already active files on the computer’
They aren’t necessarily already active, something that triggers the activity effectively triggers the avast file shield to scan them before allowing that activity or blocks if infected.
As you can hopefully see the on-demand scans are somewhat redundant because as soon as a file become active it is scanned by the File System Shield. I generally don’t run on-demand scans, usually it is only to respond to questions in the forums.