How to check if a file contains a virus

Downloading files from the internet or opening new apps is something a lot of people do on their computers on a daily basis. Some need PDFs to study, some get images they like from the web, and others just need a new app to get stuff done quickly.

However, you often hear that unknown files – or files from unknown sources – might be dangerous. That’s not an overstatement. Many viruses lurk on the internet and can be embedded into innocent-looking file which then to try to steal your data, extort you of your money, or maybe use your PC for some nefarious business.

Fortunately, there are simple ways to prevent that from happening. Of course, you can simply download antivirus software, which will keep you safe and secure – especially if you choose one from our lost of the best antivirus software. This stuff doesn’t even have to cost money: we’ve also put together a roundup of the best free antivirus.

However, if you just want to scan a single file there are other methods, even if a full security suite excels at protecting your PC (and phone) as a whole. Plus, even the best antivirus will use only its own virus database. Sometimes you might want a second opinion especially when you have a file that does look very suspicious and you want it to be checked out thoroughly.

How to run a virus scan

First, let’s start with a thorough virus scan. Maybe you’ve just downloaded something you really need from a sketchy website, and you’re a bit worried about opening it. Or you got a weird email with a strange PDF file which sounds important, but you’re not sure whether you should trust the sender.

That’s when sites such as Virustotal come into play. It’s a great website that allows you to upload a file that you’re worried about and scan it using over 70 different scanners and virus databases, making it one of the most thorough ways of checking a file’s safety. It’s extremely easy to use too!

The website allows you to upload various file formats, such as .exe files, PDFs, videos, and pictures, and analyse them using over scores of virus databases from reputable sources. It detects all kinds of unwanted “guests”: viruses, Trojans, worms and more.

Scanning engines include Bitdefender, Kaspersky, Avast, McAfee, Malwarebytes and many more names you will have heard of. It’s a bit like having all of them installed on your PC without the performance hit. Virustotal has been around since 2007 but was acquired in 2012 by Google, so you don’t have to worry about the legitimacy of that site. It’s a safe place to check if your files are safe.

Of course, there is a caveat. Virustotal is useful only for checking single files. Plus, larger files can take few minutes to analyse, so checking your whole file library one by one would be quite a chore. In that case, it’s much better to just use regular antivirus software. You also need to remember that your submission results will be shared in the app to make further improvements. That’s something to keep in mind when submitting potentially sensitive files.

To use it, you simply click on Choose file option and upload the thing that you want to scan. It takes a moment to upload and scan your file with all the databases, but in a matter of seconds, you should get your results.

When you’ve scanned a file, you can see how many of the engines detected a problem, a ‘safe-o-meter’ for quickly gauging if a file is safe, and you can also click on the tabs to check out detailed information such as the product and company name, version numbers, original file name and a whole lot more that you probably have little need for.

For common files, such as executables (.exe files), you’ll probably see a pop-up that tells you that the file has already been analysed recently. You can either click on the ‘View last analysis button’ or – if the most recent date was months ago – you can click Reanalyse to check it again.

How to quickly check if a file is safe using Microsoft Defender

However, sometimes you really don’t need to spend minutes on one file. Maybe it’s something you got from a reputable source and want to check just to be sure, or you have a hunch that something’s not right and want to quickly confirm it.

In this case, opening a dedicated website, uploading a file and waiting for 70+ results is a bit too much hassle – even if it is thorough and quite straightforward. Fortunately, if you’re on a Windows PC, things can get much simpler thanks to Microsoft Defender – a built-in basic antivirus that not only does real-time protection but can also quickly scan your files for you.

Of course, it’ll not be as exhaustive of a search as one done with Virustotal, but it’s a quick way of spotting the more obvious threats. It’s also really handy, always being just a few clicks away. Here’s how to use it: