Free Antivirus: Comodo

Comodo are better known for their firewall but they also offer free antivirus protection. Comodo is a veteran of the game having been around since 1998 with expertise in Firewall and Antivirus protection. The Comodo companies offer many free products through their website, available for public download. Most notable of Comodo's free products is the Comodo Internet Security freeware program, incorporating Comodo's firewall, Comodo Firewall Pro, Host Intrusion Prevention System and antivirus.

Free Antivirus: Immunet

Immunet is a unique cloud based antivirus system. It is very small, fast and efficient using only around 10MB to store its ClamAV antivirus engine. All virus definition files are stored on a cloud server and are matched from the hosts pc to the server to determine whether infection has taken place or not.

Free Antivirus: Avira

Avira is very well used antivirus program, the likes of Ashampoo, Ad-Aware and Webroot Web Washer all use Avira's antivirus engine to provide their services. And obviously Avira use it to provide their own free and paid antivirus services. Avira has an impressive 100 million users at the last accurate count in 2009. 

Free Antivirus: Avast!

Avast antivirus software is a veteran of the internet security world. Having been around since 1988 it has accumulated a staggering 165 million users. It has been awarded multiple awards for the excellent protection it offers. Avast, much like AVG, offer a 'reduced' free version which doesn't pack all the helpful features of paid antivirus protection but still gives you all the protection you need.

Free Antivirus: Microsoft Security Essentials

Microsoft Security Essentials, sometimes shortened to MSE is relatively new to the antivirus market. Having only been around for about 2 years it hasn't fully established itself. And yet the experts at Microsoft have been plugging away with security for Windows based operating systems for decades. It therefore makes logically sense that Microsoft know well how to protect Windows operating systems since they are the creators of it.

Free Antivirus: AVG

AVG is a well known software suite bringing anti-virus defence for either a paid or free service. Obviously we are talking about the free service. The software is developed for Windows, Linus and Mac OS X operating systems so everyone is sure to have compatibility.