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So you have an antivirus program guarding your system, your firewall is up, your browser is updated, and you’re not missing any security patches. But how can be sure your defenses are actually working as well as you think they are?

These tools can also be particularly useful if you’re trying to quickly determine how secure someone else’s PC is. They can show you just how much vulnerable software the PC has installed.

Test Your Antivirus

No, we’re not going to recommend downloading a virus to test your antivirus program — that’s a recipe for disaster. If you ever want to test your antivirus software, you can use the EICAR test file. The EICAR test file isn’t an actual virus — it’s just a text file containing a string of harmless code that prints the text “EICAR-STANDARD-ANTIVIRUS-TEST-FILE!” if you run it in DOS. However, antivirus programs are all trained to recognize the EICAR file as a virus and respond to it just as they would respond to an actual virus.

RELATED: What's the Best Antivirus for Windows 10 and 11? (Is Microsoft Defender Good Enough?)

You can use the EICAR file to test your real-time antivirus scanner and ensure it’s going to catch new viruses, but it can also be used to test other types of antivirus protection. For example, if you’re running antivirus software on a Linux mail server and you want to test that it’s working properly, you can email the EICAR file through the mail server and ensure it’s caught and quarantined.

Note: It’s important to test and make sure all your defenses are correctly configured and working properly, but this can’t guarantee your anti-virus will catch every new virus. Since there are new viruses every day, it pays to still be vigilant about what you download.

You can download an EICAR test file from the EICAR website. However, you could also create your own EICAR test file by opening a text editor (such as Notepad), copy-pasting the following text into the file, and then saving it:


Your antivirus program should react as though you had just created an actual virus.

EICAR test file quarantined by Microsoft Defender.

Port Scan Your Firewall

If you’re behind a router, the router’s network address translation (NAT) feature effectively acts as a firewall, preventing other computers on the Internet from connecting to your computer. To ensure that your computer’s software is sheltered from the Internet — either with a NAT router or through a software firewall if your computer is connected directly to the Internet — you can use the ShieldsUP! test website. It will perform a port scan of your IP address, determining whether ports are open or closed at your address. You want ports to be closed to protect potentially vulnerable services from the wild west environment of the open Internet.

RELATED: How to Port Forward on Your Router

Check Browser Extensions

Browser extensions aren’t as vulnerable as old browser plug-ins (especially Java and Flash) were, but you still need to keep an eye on them.

RELATED: What Is a Browser Extension?

Browser extensions only function because they can read and modify the content of the webpage you’re interacting with. The privacy and security implications of that are huge — every time you download and install a browser extension, you’re trusting that the author hasn’t included something malicious.

Of course, some browser extensions — maybe even most — are perfectly safe to use, but without auditing the code yourself, you can’t really be sure. If you’re going to use a browser extension, try to stick with extensions that have lots of users, and no complaints about malicious behavior. Additionally, make sure that the permissions the extension requests make sense for the service it provides. As an example, there is no reason for an adblocking extension to need access to your microphone and webcam; if you notice something like that, you should reconsider installing that extension.

Update Your Software

On operating systems with central software repositories (like Linux) or app stores (like iOS, Android, and the Microsoft Store found on newer versions of Windows), it’s easy to tell that all your applications are up-to-date with the latest released security patches. It’s all handled through a single tool that finds updates automatically.

Most applications installed on Windows computers don’t have that luxury. They’re not installed through the Microsoft Store, and the updates are handled on an application-by-application basis. Luckily, a majority of applications will automatically check for their own updates. Generally, you should allow them to update unless you have a specific reason to avoid an update.

Any applications that are primarily designed to send information over the Internet (like chat apps, browsers, VPNs, etc) should be updated more often. Their updates are much more likely to contain essential security fixes.

Of course, this doesn’t cover everything. There’s no way to ensure your antivirus will catch every virus ever created  — it won’t because no antivirus is perfect. There’s no way to ensure you won’t fall prey to phishing or another social-engineering attack. But these tools will help you test some of your most important defenses and ensure they’re ready for an assault.

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Profile Photo for Chris Hoffman Chris Hoffman
Chris Hoffman is Editor-in-Chief of How-To Geek. He's written about technology for over a decade and was a PCWorld columnist for two years. Chris has written for The New York Times and Reader's Digest, been interviewed as a technology expert on TV stations like Miami's NBC 6, and had his work covered by news outlets like the BBC. Since 2011, Chris has written over 2,000 articles that have been read more than one billion times---and that's just here at How-To Geek.
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Profile Photo for Nick Lewis Nick Lewis
Nick Lewis is a staff writer for How-To Geek. He has been using computers for 20 years --- tinkering with everything from the UI to the Windows registry to device firmware. Before How-To Geek, he used Python and C++ as a freelance programmer. In college, Nick made extensive use of Fortran while pursuing a physics degree.
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