With the release of Windows 7, many security features were introduced and it was to date the most secure OS released by Microsoft. Well Microsoft keeps on innovating in the area of security, and Windows 8 is no exception. Windows 8 will protect you from unauthorised programs that could modify the boot process of your machine, causing a malware based OS loader to start Windows normally. You will not realise that your system has been compromised because the malware was running before Windows was loaded. Your antivirus (and even Windows) knows nothing about the malware.
Introducing the UEFI which is a modern replacement for your BIOS. UEFI uses a Secure Boot feature that ensures only valid, signed operating systems get loaded. It is this feature that Windows 8 takes advantage of with Trusted Boot. Trusted boot protects drivers and system files in Windows 8. The precursor to this technology obviously started in Windows 7 and has been supercharged in Windows 8. Did you know that if you deleted Notepad in Windows 7, it will be restored within a few minutes? Windows 7 considers Notepad as essential and a copy of it is stored in a secure part of the OS.
Microsoft then extended this technology to work with securing critical .dll and system files. During the boot process, Windows 8 scans every file loaded during this phase (It also scans the usual files targeted by malware). If any of these files have been modified in any way, Windows 8 copies the actual file back, replacing the malformed file and continues to boot normally. Windows 8 even identifies legitimate anti-virus programs from reputable companies and loads these AV drivers first. This is because virus writers have used this trick to load the virus drivers and system commands before any anti-virus programs. Therefore any virus that tries to use the first-load trick is detected by the Anti-virus program.
For a great video demo of Trusted Boot, see the clip below by Stephen Rose, Senior Product Marketing Manager for Microsoft. The clip was originally posted on Demo Showcase Suite.