Microsoft has released a patch and a tool that eliminate a security vulnerability in Microsoft® Windows® 2000. The vulnerability could make it easier for a malicious user who hadcomplete control over a Windows 2000 machine to compromise users' sensitive information. A Protected Store is provided as part of CryptoAPI, in order to provide secure storage for sensitive information such as private keysand certificates. By design, the Protected Store should always encrypt the information using the strongest cryptography available on the machine. However, the Windows 2000 implementation uses 40-bit key to encrypt the Protected Store, even if stronger cryptography is installed onthe machine. This vulnerability weakens the protection onthe Protected Store, but does not eliminate it. An attacker would need to gain complete administrative control over the machine that houses the Protected Store in order to gainaccess to it, and even then would still need to mount a brute-force cryptographic attack against it. However, customers who follow the recommended remediation for this vulnerabilitycan ensure that such an attack would be significantly more difficult, if not impossible. The patch package to eliminate this vulnerability contains a new version of PBASE.DLL, the module that provides the Protected Store functionality, and a tool named Keymigrt.exe. Installing PBASE.DLL will ensure that all future additions to theProtected Store are encrypted using the strongest cryptography available on the machine. However, the Keymigrt tool also needs to be run, in order to re-encrypt all items currently in the Protected Store. We recommend that system administrators place the Keymigrt tool into users' logonscripts to ensure that the tool is run the next time they log on.