Windows Defender and Security Essentials are nearly similar on reactive, but a bit different (5%?) on Proactive. I was under the assumption that WD was just SE in Windows 8, using the same engine. Could it be a margin of error, or are they that different? I am not sure on this.
Corrine, any clarification? I haven't really done a lot of studying up on anti-virus in the past year or so!
Windows Defender on Windows 8 does use the same definitions as Microsoft Security Essentials and Microsoft Forefront. The difference is that Windows Defender on Windows 8 will interface with Windows secured boot. On a PC that supports UEFI-based Secure Boot, Windows secured boot will help ensure that all firmware and firmware updates are secure. By loading only properly signed and validated code in the boot path, the entire Windows boot path up to the anti-malware driver will be checked to ensure that it has not been tampered with.