Sound Enterprise StrategiesA number of best practices when using Encrypted File System should be incorporated into your overall public key strategy, regardless of the size of your enterprise. Best practices for the use of certificate services and EFS will be provided in Chapter 12.Here are general best practices:Clear pagefile at shut down Sensitive information such as passwords and plaintext copies of data in encrypted files may remain in the pagefile. To ensure that an offline attacker cannot recover this information, clear the pagefile at shutdown.Encrypt temporary folders Many applications, including Microsoft Word, use temporary files to store changes to documents. If the temporary files used while modifying encrypted files are not themselves encrypted, there is a risk that they might be used to discover sensitive information.Use certificates issued by CAs It is not possible to successfully manage recovery of EFS-encrypted files without using a domain-based policy that incorporates PKI.Use more than one Data Recovery Agent per domain This allows backup in the event that recovery agent keys are damaged or lost. It also allows segmentation of encryption domains. That is, the person who is authorized to recover data belonging to the Production department can be a different person from the one authorized to recover data belonging to the Accounting department.Store the private keys of the DRAs on a disk, not on a production machine Private keys stored offline can be protected from a network-based attack.Use a Central Recovery workstation Isolating data under recovery can prevent data leaks during the process. Best practices for mobile users include the following:Provide physical protection If a laptop is lost or stolen, it eventually may be possible for an attacker to read the content of encrypted files.Join the computers to the domain Centralized management and recovery is possible in a domain environment, and there is less risk.Remove private keys from the machine and keep them separate, importing them when necessary to decrypt data Although extreme, this policy will help protect data files if mobile systems are lost or stolen.Encrypt the My Documents folder.Encrypt the temporary folders.Always create new files in an encrypted folder Don't create in plain text and then encrypt.Use offline folder encryption if offline folders are used.Use Syskey in Mode 2 or Mode 3 (password on boot floppy or manual password entry required) Using Syskey in this manner prevents the computer from being booted unless the boot floppy is inserted into the floppy drive or the password is entered at the console during boot. For an excellent overview of EFS in Windows XP and Server 2003, see the "Encrypting File System in Windows XP and Windows Server 2003" white paper at http://www.microsoft.com/technet/prodtechnol/winxppro/deploy/cryptfs.mspx. |