Keeping your Windows PC secure from viruses and malware is an essential part of being a Windows user. Microsoft has the Windows Security app built-in, but you might prefer something else. However, have you thought of going open-source to secure your system?

There are good reasons to go with free and open-source alternatives to commercial software. In many cases, it’s better, and it is typically free. For instance, there are feature-rich open-source alternatives to PhotoShop to save money. If you use Windows, Linux, or even macOS, you might be looking for a free antivirus alternative backed by the open-source community.

5 ClamWin Free Antivirus

An oldie but goodie

screenshot showing ClamWin updating virus signatures on a Windows PC

In the XP days, paid antivirus apps like TrendMicro, McAfee, and Norton were common security software suites that came free on your PC with a free trial period. However, once the trial ended, they were essentially "nagware” and broke your computer. While doing tech support, a customer asked about an open-source solution. I discovered ClamWin and was so impressed that I started using it on my XP system. It’s still free and open-source under the GNU GPL. It doesn’t win any awards for an elegant modern UI, but it gets your scans and malware protection done. However, it lacks real-time scanning, but its database is regularly updated. You need to run a virus scan from the app manually to ensure a secure Windows system.

4 Armadito Antivirus

A cross-platform security solution

screenshot showing armadito antivirus running a scan for malware

Another free and open-source alternative to paid security suites is Armado Antivirus. What makes this one unique is that it’s multi-platform, meaning it works on Windows and Linux PCs and servers. One of the notable benefits of ClamWin is it offers real-time protection. It has an intuitive and responsive interface and protects your system from viruses through on-demand scans and virus quarantines. It includes tabs you would expect, like “Scan” and “Status.” It also includes a “Journal” tab that provides you with a list of Armadito activities like quarantined files, app updates, and which user was using during the time of each entry.

3 ClamAntiVirus (ClamAV)

A multi-platform alternative

screenshot-showing-clamav-logo-on-app-download-page

While Armadito is cross-platform, ClamAV goes the extra mile with multi-platform support for Windows, Linux, and macOS. It has a massive database that is updated regularly with signature-based detection of viruses, trojans, rootkits, worms, and other types of malware. It has user-friendly controls for scheduling folder scans, permitting trusted apps, and deleting suspicious files.

2 The OpenAntivirus Project

Includes email filtering

screenshot of OpenAntivirus Project main webpage

Another option is the OpenAntivirus Project, a collaborative open-source alternative that provides a virus scanner, disinfection tools, and an email filter. Unfortunately, the project is not actively maintained; however, many users still utilize it. It also has source servers as a foundation for several modern open-antivirus efforts. It offers a modern design and is cross-platform, working with Windows and Linux. It provides virus detection via signatures, pattern matching, and community-driven development.

1 MoonSecure Antivirus

Open-source antivirus for Windows

screenshot showing moonsecure antivirus running on Windows

MoonSecure AV is a straightforward security software suite that has a user-friendly GUI that first-time users will find easy to use. Another benefit is it is light on system resources, making it a good choice for low-end PCs. The Enterprise version is scalable to protect one or multiple PCs remotely on a network. In addition to virus and malware protection, it includes a firewall and support for on-demand system scanning.

Free open-source antivirus protection on multiple platforms

If you want a way to protect your PC or Mac from viruses and other malware, there are some good open-source options to consider. Personally, I have a soft spot for ClamWin since I am a Windows user. It doesn’t have real-time scanning, but it’s nice to have it in my security toolbox so I can get a second opinion if I am not completely satisfied with the Windows Security app results when I run a manual virus scan on Windows 11.