The best way to add virus scanning to Chrome and Firefox with VT4Browsers

VirusTotal’s Chrome and Firefox extensions give your web browser an integrated on-demand virus scanner for downloads and links. Let’s look at their key features for home users.

VirusTotal is one of the truly online virus scanners. You upload a suspicious file or paste a suspicious URL into its web interface, and VirusTotal runs it past more than 70 different website scanners, analysis tools, blocklists, malware detection engines from different security software makers, from MalwareBytes to Baidu.

Called VT4Browsers, the browser plug-in version is available for Firefox and Chrome, and will run on other Firefox derivatives and Chromium-based browsers. The extensions can automatically scan files you download and provide right-click menu options that you can use to check websites and scan links before you click on them, making it easy to identify dodgy links before you click on them.

VT4Browsers isn’t designed to be a substitute for the real-time protection built into Windows and macOS operating systems, or for third-party antivirus tools, but it provides a useful additional layer of protection. Linux users, particularly those who deal with a lot of files destined for use on other operating systems, will also find it helpful.

VT4Browsers won’t stop you from downloading or visiting malicious files and websites, but it will provide you with the information you need to made informed decisions about some of the more dubious things you encounter on the web.

By default, VT4Browsers automatically uploads and scans all executable file downloads except documents – it lists DOCX, DOC, XLS, XLSX, PDF as examples. It’s not mentioned, but images are also omitted by default – I was even able to download an image with an embedded RAR file.

This is for the sake of privacy, as documents and photos are more likely to include confidential information that you wouldn’t want to share with a third party such as VirusTotal. It’s also configured to confirm that you wish to upload any other non-executable files, such as compressed archives or images.

I prefer to have VirusTotal ask before it scans any files and allow me to choose exactly what I do and don’t wish to submit, so I turned off the “Don’t scan documents” restriction and enabled the “Show ‘Send to VirusTotal’ prompt” for all downloads. However, you just want something to run in the background and provide a decent balance between security and privacy without too much interaction, the default settings are fine.

The last option that’s enabled by default is the automatic submission of “anonymous passive DNS data” which will “will share with VirusTotal domain name to IP address mappings for any DNS resolutions that your browser performs.” That means that the extension will send back data about what IP address is pointed to by the domain name of every website you visit and web resource a site loads in the background.

This data is used to help identify patterns in the spread of malware online. It’s anonymised and each site’s DNS resolution data is submitted discretely, but is nonetheless something you may wish to disable if privacy and online anonymity are your top priority.

This setting will automatically submit to VirusTotal the domain name to IP address mappings for any resolutions that your browser performs, be it websites that you visit or any resources that these websites request.

Installation works much as any other browser extension – open the version for your browser in the official add-on store and click the add or install button. However, I had to restart my browser, open VT4Browsers and re-save my configuration before VT4Browsers started working fully on both Firefox and Chromium for Linux.

When it scans a file, a pop-up appears at the top right of your browser window until dismissed, with a link to the VirusTotal report. There’s even an optional configuration settings that automatically pauses the download to your PC until VirusTotal has scanned it, when a “resume download” button will appear in the results. The file will download automatically if you don’t interact with the VT4Browsers results pop-up within two minutes.

Note that VT4Browsers will not prevent you from downloading files found to be malicious – you’ll have to make that decision for yourself based on the results you get. These are fortunately easy to read, with bright red alert text for every malware detection engine that identified your suspicious object as a threat.

For its scan, VirusTotal pulls the file directly from the website you’re getting it from, rather than requiring you to upload it, so there are no additional bandwidth overheads for you.

VirusTotal is part of Google’s Chronicle Security subsidiary and runs scans on Google’s cloud infrastructure, which means all the scanning happens off your computer. As with internet bandwidth, there’s no need to worry about your system resources.