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Angela Fleischmann
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windows/security/information-protection/tpm/how-windows-uses-the-tpm.md
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@ -133,7 +133,7 @@ Mobile device management (MDM) solutions can receive simple security assertions
## Credential Guard
Credential Guard is a new feature in Windows that helps protect Windows credentials in organizations that have deployed AD DS. Historically, a user's credentials (e.g., logon password) were hashed to generate an authorization token. The user employed the token to access resources that he or she was permitted to use. One weakness of the token model is that malware that had access to the operating system kernel could look through the computer's memory and harvest all the access tokens currently in use. The attacker could then use harvested tokens to log on to other machines and collect more credentials. This kind of attack is called a "pass the hash" attack, a malware technique that infects one machine to infect many machines across an organization.
Credential Guard is a new feature in Windows that helps protect Windows credentials in organizations that have deployed AD DS. Historically, a user's credentials (such as a logon password) were hashed to generate an authorization token. The user employed the token to access resources that he or she was permitted to use. One weakness of the token model is that malware that had access to the operating system kernel could look through the computer's memory and harvest all the access tokens currently in use. The attacker could then use harvested tokens to log on to other machines and collect more credentials. This kind of attack is called a "pass the hash" attack, a malware technique that infects one machine to infect many machines across an organization.
Similar to the way Microsoft Hyper-V keeps virtual machines (VMs) separate from one another, Credential Guard uses virtualization to isolate the process that hashes credentials in a memory area that the operating system kernel cannot access. This isolated memory area is initialized and protected during the boot process so that components in the larger operating system environment cannot tamper with it. Credential Guard uses the TPM to protect its keys with TPM measurements, so they are accessible only during the boot process step when the separate region is initialized; they are not available for the normal operating system kernel. The local security authority code in the Windows kernel interacts with the isolated memory area by passing in credentials and receiving single-use authorization tokens in return.