Spyware, Viruses, & Security forum

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Scanning downloaded files

by Bill Osler / December 23, 2008 8:07 PM PST

There is a Firefox option to skip scanning of downloaded files. Disabling this scan nominally speeds up the browser a bit.
I'm using AVG 8 on Win XP Pro, browsing with FF 3.
I presume that AVG scans all files when they are opened, so scanning files on download does seem redundant. Or am I missing something?
The Firefox key in question is browser.download.manager.scanWhenDone and the default value is True. I have not changed it, but I do wonder whether this extra scan adds anything from a security perspective.

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That's Your Virus Scanner Function..
by Grif Thomas Forum moderator / December 24, 2008 3:49 AM PST

If you make that particular setting "False", it will prevent your antivirus from scanning downloaded files in Firefox.. NOT a good thing unless you really feel like you want to manually RIGHT click on every downloaded file and scan it with your antivirus program. Generally, you DON'T want to wait for the downloaded file to be opened but instead want it scanned when it's "saved" to the computer.. The value also indicates whether downloaded files trigger a security warning upon launch. I recommend leaving it enabled/True.. but it's your choice.

Read the link below for the basic information about "browser.download.manager.scanWhenDone":


Hope this helps.


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Thanks ...
by Bill Osler / December 24, 2008 4:29 AM PST

I discovered something troubling while messing with this. I don't know if it is a configuration problem or not.
I have AVG 8 installed with all available updates. FF 3 is set for default behavior (scan when download is finished). I am not receiving any warning messages when I download the test file from http://www.eicar.org/anti_virus_test_file.htm
I DO receive a warning when I try to open the eicar test file. I also receive a warning if I manually scan the downloaded file.
When I try to download the eicar.com file with IE 6 I get a warning almost immediately.
I get no warning with either browser when I download eicar.txt or one of the zipped versions.
Very strange.

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That's A Problem With Your Antivirus Program..
by Grif Thomas Forum moderator / December 25, 2008 4:44 AM PST
In reply to: Thanks ...

A number of antivirus programs are unable to correctly identify the zipped forms of EICAR when using the browser.. At the same time, they will almost always detect the test virus when doing a manual scan on the downloaded file.. Certainly, that's not a good thing but it's not unusual.. It most certainly tells you that the manual scan does a better job at detecting malware than the background scanner.

Hope this helps.


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