Microsoft is tweaking its Windows Defender tool, which has been part of the last few versions of Windows, by essentially adding some of the more robust features from its free Security Essentials product. Steven Sinofsky, president of the Windows and Windows Live division, said "we've taken Defender, and we've actually built a whole new range of protection, all the way up through anti-malware, antivirus, all that is built into Defender."
This may not be a good idea since it could be a false sense of security for Windows 8 users who may have normally installed third party security products on their computers. It may also make for a focus point for virus and spyware creators to try and bypass. Roel Schouwenberg from Kaspersky Lab thinks this could be dangerous. "From a technical perspective this would mean malware authors will make sure their creations go undetected by MSE/Defender before deployment".
Researchers at Symantec examined an early build and confirmed that the new Windows Defender definitely is just a repackaged version of Microsoft Security Essentials. Test results by major independent labs show Microsoft Security Essentials rated good but not great.
The protection consumers need is more comprehensive than what basic antivirus offers these days thanks to more advanced tactics from malware creators. A pre installed antivirus product doesn't compare to the type of robust solutions you see today.