Microsoft launched "Security Essentials", an anti-virus or anti-malware software... It is totally free to update. And Offers real-time protection against any type of viruses, spyware, and other malicious programs.
There are lots of Anti-Virus available for free over internet but the company like Microsoft can create such Free Anti-Virus is quite strange? This can be said that more effective protection will be given by this anti-virus software by Microsoft.