Antivirus software is designed to help detect, prevent, and remove malware, including viruses, from your devices. Open-source antivirus programs can protect your computer against viruses at little to no expense.

However, there’s a limited selection of open-source antivirus software available, and not all of them can effectively protect your PC from viruses. Here are the top ones.

1. MoonSecure Antivirus

MoonSecure is a free and open-source antivirus software for Windows. It’s an enterprise-grade program that’s easy to install and consumes little resources.

The antivirus software is scalable, allowing you to protect one or thousands of PCs from viruses. It also prevents running apps from USBs and logs events.

MoonSecure’s main features include a firewall, NetShield, and support for on-access scanning. It offers real-time scanning and lets you perform quick and deep scans, so if you're worried about being infected, you can scour your system with ease.

2. ClamWin

ClamWin is a free antivirus for Windows that boasts hundreds of thousands of users worldwide. It’s built on ClamAV scanning engine and uses an open-source license, the GNU General Public License (GPL).

The software is easy to install and use, and has a regularly updated database, which is how security suites keep track of malware. It, however, lacks an on-access real-time scanner.

To detect viruses or spyware in a file, you’ll need to scan it manually; fortunately, the program allows you to schedule regular scans. It can identify rootkits as well.

ClamWin can prevent malicious files from executing and move them to a specified quarantine folder. In addition, it features a Microsoft Outlook add-on that helps remove virus-infected attachments.

3. Clam AntiVirus

ClamAntiVirus (ClamAV) is a cross-platform, open-source antivirus engine for detecting malware. It’s one of the most popular antivirus suites that work with Linux, Windows, and macOS.

ClamAV has a huge virus database that receives regular updates and uses a signature-based system to detect Trojans, worms, rootkits, and other malware. Plus, it allows you to schedule folder scans, whitelist trusted software, and configure it to delete suspicious files, so is particularly useful.

You can use the antivirus to scan mail servers for malware and spam messages. It supports all standard mail file formats and is compatible with multiple mail transfer agents like Microsoft Outlook and Sendmail.

It further supports multiple archive formats like ZIP, RAR, and Tar, as well as document formats such as MS Office, PDF, Flash, and HTML.

4. Armadito Antivirus

Armadito Antivirus is another open-source and multi-platform antivirus option that aims to protect Windows and Linux PCs and servers from viruses.

The antivirus suite has an intuitive and user-friendly interface that lets you access features like quarantine, on-demand scanning, and real-time protection. Notably, it offers real-time detection on the free and open-source GNU/Linux and MS Windows.

The interface is particularly friendly and easy to use. Primarily, there are three main tabs: Status, Scan, and Journal. It defaults to the first one, giving you a solid overview of your protection levels; the Scan option does exactly what it says on the tin, guiding you through what has been checked and whether anything malicious has been found; and the Journal tab gives you a list of all Armadito Antivirus activities (like quarantined files, and app or system updates), including who was using it at the time of each entry.

Open-Source Antivirus Programs Have Pros and Cons

One main advantage of open-source antivirus programs is that anyone can see the source code and even edit it! Because of that, errors are often identified and fixed quickly. However, malicious actors can leverage this accessibility to insert malicious elements into the source code, putting users at risk. So open-source software isn't for everyone, but is certainly worth thinking about.