Software giant Microsoft has said that it will block pirates from downloading its free AV software.

Security Essentials is basic anti-virus and anti-spyware software that Microsoft touts as suitable for users who can't, or won't, pay for security. However Alex Kochis, director of Microsoft's Genuine Windows team said that people will be asked to validate Windows running on their PC to make sure that it's genuine before they are allowed to download.

PCs that fail the validation check will display a second dialog that provides a link to the section of Microsoft's site where users can buy Windows. Although Microsoft blocks pirates from downloading other free software it offers, it regularly makes major exceptions. Internet Explorer 8 can be downloaded and installed on a counterfeit copy of Windows.  People running bogus copies Windows obtain security patches via Windows Update.

John Pescatore, Gartner's primary security analyst has backed Microsoft's move, saying he could not see any justification for making Microsoft give away Security Essentials to counterfeit Windows users. This is mostly because people have many other choices, including free AV software.