VirusTotal lets you scan a file for malicious programs that might come bundled with an otherwise trustworthy app. We normally download an app and then scan it via the VirusTotal website. The scan is accurate but if it could come before a file is downloaded, it can save us time. Download Virus Checker is a Firefox add-on and a Chrome extension that scans a file via the VirusTotal API before it begins to download.
Install Download Virus Checker and start downloading a file. The add-on adds a bug icon to the toolbar and it shows you the number of active scans. When you start a download, the icon will show a number badge to indicate a scan is in progress.
Click the icon to see how many scans are in progress.
The download starts after the scan is complete. If you download a file from a trusted source, e.g. VLC from the official website, the scan will complete much sooner than it would have had you downloaded the file and then uploaded it to VirusTotal.
By default, the add-on will tell you the file you’re downloading is malicious if it fails to get a clean bill of health from at least three antivirus programs. It will also skip scanning video, audio, and plain text files. You can change these settings from the add-on’s options.
Visit Download Virus Checker’s options and change the number of positive reports needed for the add-on to alert you that the file you’re downloading could be malicious. If you’ve used VirusTotal a lot, you know it sometimes gives false positives. This setting is meant to deal with that. You can increase or decrease the number of false positives that are acceptable.
You can also specify file types that should not be scanned. In addition to excluding audio, video, and plain text, you can also exclude images. It’s probably not a good idea to exclude zipped files i.e. archives.
If the add-on detects something malicious in the file you want to download, it gives you a detailed report of the problem. For Chrome users, this is an extra layer of security on top of the default scan that Chrome runs on all downloads once they are complete.