Professional Windows Server 1002003 Security A Technical Reference [Electronic resources]

Roberta Bragg

نسخه متنی -صفحه : 194/ 57

What Is the Encrypting File System?

EFS is a component of the NTFS file system that can be used to encrypt data files. Ordinary users of Windows systems can encrypt and decrypt their data files if the following conditions are met:

The operating system is Windows 2000, Windows XP Professional, or Windows Server 2003.

The file system is NTFS.

Data files are not placed in the root or %systemroot% folders. (These areas cannot be encrypted).

Files are not marked with the System attribute. (System files cannot be encrypted.)

EFS has not been disabled.

It is not necessary for the computer to be joined in a domain, to implement certificate services, or to institute administrative management of certificates and files. However, the security of the system will be enhanced if you do these things. In fact, without such management, it is possible for data loss to occur.

Have You Implemented EFS?

At a series of Microsoft security summits for IT pros, I asked the question, "How many of you have implemented EFS?" Very few hands were raised. I told them they were liars because EFS is implemented by default. Any user can encrypt files without the benefit of administrative implementation, instruction, or management.

Therein lies a very large problem: Without training, ordinary users can live with a false sense of security, and IT pros can find themselves with data recovery problems and privacy issues.

If users do not realize access to their password allows transparent access to their encrypted files, they may use weak passwords, write their passwords down in plain view, or share passwords with coworkers and friends.

If users don't understand the necessity of backing up their private key, they may lose access to encrypted files if their profile becomes corrupt or if their system is rebuilt.

If IT pros ignore EFS while their users adopt it, IT pros may be left with critical but unrecoverable company data, find that unauthorized administrators have accidental access to sensitive data, and end up spending troubleshooting, training, maintenance, and implementation time needed for other projects fighting EFS issues.

Without doubt, important data has been lost and needless hours spent all for the want of a sound EFS policy. I cannot emphasize strongly enough that your policy toward EFS should be to disable it until you can implement a sound, practical, and recoverable EFS strategy. This chapter will provide you with the basics; Chapter 12, "PKI Basics," and Chapter 13, "Implementing a Secure PKI," provide information that can be used to develop such practices.