virus still dangerous when in windows defender quarantine

Question

So I've checked my computer and I've found an old trojan file in the quarantine-tab of windows defender.

It is there since two months. So my question is: If the file is in the quarantine, is it still harmful? Or is it save, if I just remove it now?

Answer 1

Files on quarantine are "stopped" by the antivirus software... so they are harmless. You can remove it when you want or keep it for study or whatever.

Answer 2

The virus that Windows Defender quarantined should not pose any further risk. However, you should check the source of the file (or try to infer from the path where it was found) to try and determine if it was an infected file created by a legitimate process, or if it was the result of a running infection. That will give you a better sense of whether the system is still at risk.

If the file was found in C:\User\BobSmith\Downloads\ for example, it could be a single file that was caught before it could do any damage. Run a full system scan with an alternate virus scanner (i.e. by attaching the hard drive to another system, or by booting to a live CD or USB key).

If the file was found in C:\Windows\system32\ for example, it could mean your system had a executing infection and may (almost certainly) still be compromised. In this case, backup your data and reformat the system if you need to be able to trust it again; otherwise treat it like a public internet kiosk.