Virus Check Files Online Without Downloading Them

Martin Brinkmann
Aug 10, 2010
Updated • Apr 10, 2012
Firefox, Firefox add-ons

It sometimes is a good idea to check a file online for malicious code before downloading it to the local computer system. While it is usually not dangerous to download a file as long as it is not executed, it can save some time to perform a virus scan before downloading the file.

The developers of one of the most popular online virus scanning services, Virus Total, have released a Firefox add-on today that can be used for exactly that purpose, and more.

The VTzilla Firefox plugin adds options to Firefox to scan files at the Virus Total service without downloading them to the local system first. It can furthermore scan websites and urls with popular website scanners, and search the Virus Total database for file hashes and other data.

Non-Firefox users can rejoice as well, as it is now possible to submit websites and hosted files at the Virus Total website as well, to perform the same checks that the Firefox add-on offers.


Back to the Firefox add-on. The add-on basically automates part of the process of scanning files hosted on websites for malicious code. The extension installs a toolbar, and options in the right-click menu.

The toolbar offers two interesting options. For one, the ability to search the Virus Total database. This is done by entering a keyword into the form and clicking on the Search VirusTotal button.

Users can search for file hashs (supported are md5, sha1 and sha256), urls, user accounts and user comments. There is unfortunately no option to search directly for file names.

The second button scans the website's url with various services to determine a threat level. The services currently used are the safe browsing filters of Firefox, Google and Opera, and the security services Phishtank, Smartscreen and TRUSTe.

url analysis tool
url analysis tool

The right-click context menu can be used to send urls or files directly to the Virus Total service to scan them there for viruses and other malicious contents. Most Firefox users will probably disable the Virus Total toolbar in the browser, considering that only the search option offers unique features in comparison to the context menu option.

The Firefox add-on furthermore adds an option to scan file downloads with Virus Total. This option is displayed directly in the file download window, and can be selected before the download starts.

scan with virus total
scan with virus total

The Firefox add-on has many advantages over manually using the Virus Total website. The options to initiate virus scans of a file download before starting the download, and a website before accessing it make the Firefox add-on a recommended addition for security conscious users and heavy downloaders.

VTzilla is available for download at the Virus Total website.


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  1. paul said on October 2, 2010 at 7:23 am

    That actually was me, John Mack — awaiting moderation.

    Lighten up!!!!

  2. paul said on October 2, 2010 at 7:22 am

    Nice addon

  3. John Mack said on October 2, 2010 at 7:16 am

    Useful add-on. I have the Virus Total Uploader but the problem is just downloading a file sometimes can infect your computer.

    Another virus scanning site is “Jotti’s malware scan”

  4. Jimmy said on September 25, 2010 at 3:43 pm

    Thank you for the addon

  5. BosseWeb said on August 11, 2010 at 8:32 pm

    VirusTotal has its own freeware for doing something similar: VirusTotal Uploader. It can be found on:

    1. Martin said on August 11, 2010 at 9:10 pm

      Thanks Bosse, we have reviewed the Virus Total Uploader previously here

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