Avast Free Antivirus
Avast Free Antivirus is a suite of antimalware and personal data-security tools, ranging from the antivirus scanner to a password manager and a software update checker. Avast Software purchased its competitor AVG Technologies in October 2016. While the two brands remain separate, their respective antivirus suites now have some design language in common.
AVG Internet Security
AVG AntiVirus FREE is once-again a powerhouse of an antivirus. This essential security suite will protect your computer against viruses, worms, trojans, root-kits, and other spyware when browsing online or checking your email. AVG AntiVirus FREE is able to block infected links as you browse, checks files before you download them, and help you protect your personal data online and on your PC with an solid set of privacy features.
Avira Free Antivirus
Avira Free Antivirus is one of best free antivirus software programs out there for various reasons, the least of which is just because it's free. My favorite feature of Avira Free Antivirus is the wide range of malware threats that it protects you from. I also like how simple the interface is. Important: Avira Free Antivirus provides free on-access or resident protection, meaning it's keeping an eye on things all the time.
ClamAV Free Antivirus
Clam AntiVirus (ClamAV) is a free, cross-platform and open-source antivirus software toolkit able to detect many types of malicious software, including viruses. One of its main uses is on mail servers as a server-side email virus scanner. The application was developed for Unix and has third party versions available for AIX, BSD, HP-UX, Linux, macOS, OpenVMS, OSF (Tru64) and Solaris. As of version 0.97.5, ClamAV builds and runs on Microsoft Windows. Both ClamAV and its updates are made available free of charge.
Microsoft Security Essentials
Microsoft Security Essentials is easily one of the best free antivirus program available. I like it because it's produced by Microsoft and because it's really easy to see if the program is protecting you as it should be. Microsoft Security Essentials provides constant virus protection, also called on-access or resident protection, for free. This means that Microsoft Security Essentials can completely replace antivirus software from companies like McAfee and Norton that charge for their software and for yearly access to updates.