Expert's Guide to Windows 7 Security
Windows 7 has been warmly received and swiftly adopted by businesses, with the result that many IT admins are now struggling with the platform's new security features. In addition to changes to User Account Control, BitLocker, and other features inherited from Windows Vista, Windows 7 introduces a slew of new security capabilities that businesses will want to take advantage of.
Windows 7 improves on Vista with a friendlier UAC mechanism, the ability to encrypt removable media as well as hard drive volumes, broader support for strong cryptographic ciphers, hassle-free secure remote access, and sophisticated protection against Trojan malware in the form of AppLocker, to name just a few.
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In this guide, I'll run through these and other significant security enhancements in Windows 7, and provide my recommendations for configuring and using them. I'll pay especially close attention to the new AppLocker application-control feature, which may be a Windows shop's most practical and affordable way to combat socially engineered Trojan malware.
Windows 7 has literally hundreds of security changes and additions, far too many to cover in one fell swoop. While this guide focuses on the ones that most organizations will be interested in, keep in mind that plenty of others may deserve your attention. A few the biggies not discussed here are built-in support for smart cards and biometrics, the ability to force the use of Kerberos in a feature called Restrict NTLM, and support for the new DNSSec standards, which are becoming essential to prevent DNS exploitation attacks. Also noteworthy is a new feature called Extended Protection for Authentication, which prevents many sophisticated man-in-the-middle attacks that can strike at some of our most trusted security protocols (such as SSL and TLS).
User Account Control A Windows Vista feature that users loved to hate, User Account Control has been significantly improved to be both less intrusive and smarter at distinguishing between legitimate and potentially malicious activities in Windows 7. However, depending on whether you are logged on as administrator or a standard user, some installs of Windows 7 may have a default UAC security setting that's one level lower than some experts (including yours truly) recommend. Standard users have UAC security default to the most secure setting, while administrator accounts reside a notch below the highest setting, which is potentially riskier.
Note too that, although UAC provides a much-needed mechanism to prevent the misuse of administrator privileges, it can be bypassed. If you must have high security, users should not log on with an elevated user account until they need it.
Your domain environment should already be at the highest and most secure level ("Always notify"). If it isn't, make it so. That way, users will be prompted to input their passwords to perform high-risk administrative actions. No matter what else, UAC should be enabled.
BitLocker drive encryption In Windows 7, BitLocker drive encryption technology is extended from OS drives and fixed data drives to include removable storage devices such as portable hard drives and USB flash drives. This new capability is called BitLocker to Go.
In Windows Vista SP1, Microsoft added official support for encrypting fixed data drives, but it could only be done using command-line tools. Now you can encrypt operating system volumes, fixed data drives, and USB flash drives with a simple right-click, via the Windows Explorer GUI. Moreover, you can use smart cards to protect data volumes, and you can set up data recovery agents to automatically back up BitLocker keys. If you're using a Trusted Platform Module (TPM) chip, you can enforce a minimum PIN length; five characters should suffice for most environments.
In Windows 7, there is no need to create separate partitions before turning on BitLocker. The system partition is automatically created and does not have a drive letter, so it is not visible in Windows Explorer and data files will not be written to it inadvertently. The system partition is smaller in Windows 7 than in Windows Vista, requiring only 100MB of space.
With BitLocker to Go, you can encrypt removable drives one at a time or require that all removable media be encrypted by default. Further, encrypted removable media can be decrypted and re-encrypted on any Windows 7 computers -- not just the one it was originally encrypted on.
BitLocker to Go Reader (bitlockertogo.exe) is a pro­gram that works on computers running Windows Vista or Windows XP, allowing you to open and view the content of removable drives that have been encrypted with BitLocker in Windows 7.
You should enable BitLocker (preferably with TPM and another factor) on portable computers if you do not use another data encryption product. Store the BitLocker PINs and recovery information in Active Directory or configure a domain-wide public key called a data recovery agent that will permit an administrator to unlock any drive encrypted with BitLocker. Require BitLocker to Go on all possible removable media drives.
Easily encrypted page file Users who cannot use BitLocker but still want to prevent the memory swap page file from being analyzed in an offline sector editing attack no longer need to erase the page file on shutdown. Windows XP and earlier versions had a setting that allowed the page file to be erased on shutdown and rebuilt on each startup. It's a great security feature, but it often caused delayed shut­downs and startups -- sometimes adding as much as 10 minutes to the process.
In Windows 7 (and Vista), you can enable page file encryption. Even better, there is no key management. Windows creates and deletes the encryption keys as needed, so there is no chance the user can "lose" the key or require a recovery. It's crypto security at its best.
Better cryptography Windows 7 includes all the latest industry-accepted ciphers, including AES (Advanced Encryption Standard), ECC (Elliptical Curve Cryptography), and the SHA-2 hash family. In fact, Windows 7 implements all of the ciphers in Suite B, a group of cryptographic algorithms that are approved by the National Security Agency and National Institute of Standards and Technology for use in general-purpose encryption software.
While Microsoft added support for Suite B cryptographic algorithms (AES, ECDSA, ECDH, SHA2) to Windows Vista, Windows 7 allows Suite B ciphers to be used with Transport Layer Security (referred to as TLS v.1.2) and Encrypting File System (EFS). Suite B ciphers should be used whenever possible. However, it's important to note that Suite B ciphers are not usually compatible with versions of Windows prior to Windows Vista.
By default, all current technologies in Windows will use industry standard ciphers in place of legacy, proprietary ciphers. Those legacy ciphers that still exist are included only for backward-compatibility purposes. Microsoft has shared the new ciphers in detail with the crypto world for analysis and evaluation. Key and hash sizes are increased by default.
EFS (Encrypting File System) has been improved in many ways beyond using more modern ciphers. For one, you can use a smart card to protect your EFS keys. This not only makes EFS keys more secure, but allows them to be portable between computers.
Administrators will be happy to know that they can prevent users from creating self-signed EFS keys. Previously, users could easily turn on EFS, which generated a self-signed EFS digital certificate if a compatible PKI server could not be found. Too often, these users encrypted files but did not back up their self-signed digital certificates, which frequently led to unrecoverable data loss.
With Windows 7, administrators can still allow self-signed EFS keys, while mandating ciphers and minimum key lengths. Windows 7 will prod users to back up their EFS digital certificates to some other removable media or network drive share -- and keep prodding them until they do it. A Microsoft Web page details the EFS changes.
Read more about how to secure your Windows 7 PCs in InfoWorld's free PDF report, "Windows 7 Security Deep Dive," including:
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