You will call it 5 Free Best Antivirus Software for PC/Linux, once if you used it in your pc. List here provides Open Source Antivirus Software and Free to use.
These free open source antivirus made their code freely available so that anyone with little knowledge can make some changes to it as their requirement.
Some best lists of open source free antivirus software are given below :
Armadito Antivirus protects your computers and servers from any malware and viruses. The solution is available for both Windows and Linux, and is composed with a web-based central administration console. It can be used remotely from anywhere through an intuitive interface, giving access to many features. Github
Open Antivirus Successful open source software always proves excellence in reliability, effectiveness, scalability, and portability. The Apache httpd, the Linux operating system and Perl as a scripting language or in the field of security OpenSSH, OpenSSL and GnuPG are prominent examples disguising that there are important fields lacking comparable solutions. One of these fields is anti-virus software.
VirusHammer: A standalone virus scanner that end users can run
ScannerDaemon: This uses command line utilities to find viruses
PatternFinder: Finds queries and sources of viruses
Squid-vscan: A software program that lets you scan all your traffic to see if it contains any known malware or viruses
Clam AntiVirus is an open source (GPL) anti-virus toolkit for UNIX, designed especially for e-mail scanning on mail gateways. It provides a number of utilities including a flexible and scalable multi-threaded daemon, a command line scanner and advanced tool for automatic database updates. It has built-in support for all standard mail file formats, various archive formats, executable formats, and popular document formats. The core of the package is an anti-virus engine available in a form of shared library.
Clam Win another open source free antivirus. ClamWin is a Free Antivirus program for Microsoft Windows 10 / 8 / 7 / Vista / XP / Me / 2000 / 98 and Windows Server 2012, 2008 and 2003. ClamWin Free Antivirus is used by more than 600,000 users worldwide on a daily basis.
Moon Secure AV : The Windows Report says Moon Secure AV is another open source antivirus tool that uses the same ClamAV engine that Armadito Antivirus also uses. Moon Secure AV does a great job at detecting viruses, Trojans, and spyware that’s found in your scan engines, Net shield, Firewall, Exec scanner, and rootkits.