Search Support

Avoid support scams. We will never ask you to call or text a phone number or share personal information. Please report suspicious activity using the “Report Abuse” option.

Learn More

Downloads with Firefox are not virus checked after download (Windows Defender)

more options

While doing some virus discovery tests with Windows Defender and other AV products I realized that with Firefox files are not scanned when download finishes. With Chrome and Edge the Windows Defender immediately checks and blocks malicious files. Not so with Firefox. Then the file is only checked and blocked when opened.

After some research I found that in the past there was an Option `browser.download.manager.scanWhenDone` but this seems no longer available. Under Security software in about:support Windows Defender seems to be correctly set.

Is there a way to have files immediately checked by the AV after download in Firefox completes?

While doing some virus discovery tests with Windows Defender and other AV products I realized that with Firefox files are not scanned when download finishes. With Chrome and Edge the Windows Defender immediately checks and blocks malicious files. Not so with Firefox. Then the file is only checked and blocked when opened. After some research I found that in the past there was an Option `browser.download.manager.scanWhenDone` but this seems no longer available. Under Security software in about:support Windows Defender seems to be correctly set. Is there a way to have files immediately checked by the AV after download in Firefox completes?

All Replies (8)

more options

The tags show Linux erroneously as I made this post from Linux. It's about Firefox on Windows of course. Can someone with sufficient rights fix the tags? It's about Windows and the latest FF Version.

Helpful?

more options

I think Defender should scan all files as they are written, but maybe the application needs to trigger that? As you probably noticed, Firefox creates a temporary placeholder and the actual download is first saved as a .part file. Can you tell whether Defender is scanning the .part file?

I removed the Linux tag; can you add your Windows version using the Tags box to the right of the question (type Win to generate matches)?

Helpful?

more options

All security software is supposed to block the EICAR test file, so you can use that to see whether it survives the on-download scan:

https://www.eicar.org/download-anti-malware-testfile/

I get a zero byte file and a yellow triangle on the Downloads button (indicates the download failed or was blocked), but I'm not using Defender.

Helpful?

more options

Helpful?

more options
@

jscher2000 - Support Volunteer said

I removed the Linux tag; can you add your Windows version using the Tags box to the right of the question (type Win to generate matches)?

I can't find a way to add tags. Tried edit this question.

Helpful?

more options

Not working

Helpful?

more options

damonsalvatorev975 said

Not working

Are you confirming the issue or what are you refering to with "not working".

Helpful?

more options

I added a tag for "Windows 10"

I can't test Defender due to having other security software (IT department managed).

Helpful?

Laajal dara

You must log in to your account to reply to posts. Please start a new question, if you do not have an account yet.