The software provides basic anti-virus protection to licensed users of the Windows operating system that automatically updates through the Windows update facility.
The free anti-virus software has been available only to consumers, but Microsoft has announced that licences for small businesses will be available from October.
"It's also no secret that most small businesses today do not have a dedicated IT professional on staff to manage their IT resources", said Eric Ligman, worldwide partner group experience lead at Microsoft.
"Microsoft Security Essentials is an excellent solution for your small business. It is very easy to get and very simple to use. The software requires no registration, trials or renewals and is available for download directly from Microsoft", he wrote in a company blog post.
But, he said, if a small business wants virus and malware protection to be centrally administered and integrated with group policy settings, Microsoft Forefront Client Security is a better option.
Since the release of Security Essentials in September 2009, commercial security software suppliers have claimed they are not concerned by Microsoft's move because free software does not have the support that the more important business market requires.
This story was first published by Computer Weekly