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Logical Asset Security

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This chapter is from the book

This chapter is from the book

Determine Data Security Controls

Any discussion on logical asset security must at some point discuss encryption. While there is certainly more to protecting data than just encrypting it, encryption is one of the primary controls used to protect data. Just consider all the cases of lost hard drives, laptops, and thumb drives that have made the news because they contained data that was not encrypted. In many cases encryption is not just a good idea; it is also mandated by law. CISSP candidates must ensure that corporate policies addressing where and how encryption will be used are well defined and being followed by all employees.

Let’s examine the two areas at which encryption can be used to protect data at a high level. These topics will be expanded on in Chapter 6, “The Application and Use of Cryptography.”

Data at Rest

Data at rest is information stored on some form of media that is not traversing a network or residing in temporary memory. Failure to properly protect data at rest can lead to attacks such as the following:

  • Pod slurping, a technique for illicitly downloading or copying data from a computer. Typically used for data exfiltration.

  • Various forms of USB (Universal Serial Bus) malware, including but not limited to USB Switchblade and Hacksaw.

  • Other forms of malicious software, including but not limited to viruses, worms, Trojans, and various types of key loggers.

Data at rest can be protected via different technical and physical hardware or software controls that should be defined in your security policy. Some hardware offers the ability to build in encryption. A relatively new hardware security device for computers is called the trusted platform module (TPM) chip. The TPM is a “slow” cryptographic hardware processor which can be used to provide a greater level of security than software encryption. A TPM chip installed on the motherboard of a client computer can also be used for system state authentication. The TPM can also be used to store the encryption keys.

The TPM measures the system and stores the measurements as it traverses through the boot sequence. When queried, the TPM will return these values signed by a local private key. These values can be used to discover the status of a platform. The recognition of the state and validation of these values is referred to as attestation. Phrased differently, attestation allows one to confirm, authenticate, or prove a system to be in a specific state. Data can also be encrypted using these values. This process is referred to as sealing a configuration. In short, the TPM is also a tamper-resistant cryptographic module that can provide a means to report the system configuration to a policy enforcer or “health monitor.”

The TPM also provides the ability to encrypt information to a specific platform configuration by calculating hashed values based on items such as the system’s firmware, configuration details, and core components of the operating system as it boots. These values, along with a secret key stored in the TPM, can be used to encrypt information and only allow it to become usable in a specific machine configuration. This process is called sealing.

The TPM is now addressed by ISO 11889-1:2009. It can also be used with other forms of data and system protection to provide a layered approach, referred to as defense in depth. For example, the TPM can help protect the actual system, while another set of encryption keys can be stored on a user’s common access card or smart card to decrypt and access the data set.

Another potential option that builds on this technology is self-encrypting hard drives (SEDs). These pieces of hardware offer many advantages over non-encrypted drives:

  • Compliance—SEDs have the ability to offer built-in encryption. This can help with compliance laws that many organizations must adhere to.

  • Strong security—SEDs make use of strong encryption. The contents of an SED are always encrypted and the encryption keys are themselves encrypted and protected in hardware.

  • Ease of use—Users only have to authenticate to the drive when the device boots up or when they change passwords/credentials. The encryption is not visible to the user.

  • Performance—As SEDs are not visible to the user and are integrated into hardware, the system operates at full performance with no impact on user productivity.

Software encryption is another protection mechanism for data at rest. There are many options available, such as EFS, BitLocker, and PGP. Software encryption can be used on specific files, databases, or even entire RAID arrays that store sensitive data. What is most important about any potential software option is that not only must the encrypted data remain secure and remain inaccessible when access controls, such as usernames and passwords, are incorrect; the encryption keys themselves must be protected, and should therefore be updated on a regular basis.

Data in Transit

Any time data is being processed or moved from one location to the next, it requires proper controls. The basic problem is that many protocols and applications send information via clear text. Services such as email, web, and FTP were not designed with security in mind and send information with few security controls and no encryption. Examples of insecure protocols include:

  • FTP—Clear-text username and password

  • Telnet—Clear-text username and password

  • HTTP—Clear text

  • SMTP—All data is passed in the clear

For data in transit that is not being protected by some form of encryption, there are many dangers, which include the following:

  • Eavesdropping

  • Sniffing

  • Hijacking

  • Data alteration

Today, many people connect to corporate networks from many different locations. Employees may connect via free Wi-Fi from coffee shops, restaurants, airports, or even hotels.

One way to protect this type of data in transit is by means of a Virtual Private Network (VPN). VPNs are used to connect devices through the public Internet. Three protocols are used to provide a tunneling mechanism in support of VPNs: Point-to-Point Tunneling Protocol (PPTP), Layer 2 Tunneling Protocol (L2TP), and IP Security (IPSec). When an appropriate protocol is defined, the VPN traffic will be encrypted. Microsoft supplies Microsoft Point-to-Point Encryption (MPPE), with PPTP, native to the Microsoft operating systems. L2TP offers no encryption, and as such is usually used with IPSec in ESP mode to protect data in transit. IPSec can provide both tunneling and encryption.

Two types of tunnels can be implemented:

  • LAN-to-LAN tunnels—Users can tunnel transparently to each other on separate LANS.

  • Host-to-LAN tunnels—Mobile users can connect to the corporate LAN.

Having an encrypted tunnel is just one part of protecting data in transit. Another important concept is that of authentication. Almost all VPNs use digital certificates as the primary means of authentication. X.509 v3 is the de facto standard. X.509 specifies certificate requirements and their contents. Much like that of a state driver’s license office, the Certificate Authority (CA) guarantees the authenticity of the certificate and its contents. These certificates act as an approval mechanism.

Just as with other services, organizations need to develop policies to define who will have access to the VPN and what encryption mechanisms will be used. It’s important that VPN policies be designed to map to the organization’s security policy. As senior management is ultimately responsible, they must approve and support this policy.

Standard email is also very insecure and can be exposed while in transit. Standard email protocols such as SMTP, POP3, and IMAP all send data via clear text. To protect email in transit you must use encryption. Email protection mechanisms include PGP, Secure Multipurpose Internet Mail Extensions (S/MIME), and Privacy Enhanced Mail (PEM). Regardless of what is being protected periodic auditing of sensitive data should be part of policy and should occur on a regular schedule.

Data in transit will also require a discussion of how the encryption will be applied. Encryption can be performed at different locations with different amounts of protection applied.

  • Link encryption—The data is encrypted through the entire communication path. Because all header information is encrypted each node must decrypt and encrypt the routing information. Source and destination address cannot be seen to someone sniffing traffic.

  • End to end encryption—Generally performed by the end user and as such can pass through each node without further processing. However, source and destination addresses are passed in clear text, so they can be seen to someone sniffing traffic.

Endpoint Security

No review of logical asset security would be complete without a discussion of endpoint security. Endpoint security consists of the controls placed on client or end user systems, such as control of USB and CD/DVD, antivirus, anti-malware, anti-spyware, and so on. The controls placed on a client system are very important.

  • Removable media—A common vector for malware propagation is via USB thumb drive. Malware such as Stuxnet, Conficker, and Flame all had the capability to spread by thumb drives. Removable drives should be restricted and turned off when possible.

  • Disk encryption—Disk encryption software such as EFS and BitLocker can be used to encrypt the contents of desktop and laptop hard drives. Also, corporate smartphones and tablets should have encryption enabled.

  • Application whitelisting—This approach only allows known good applications and software to be installed, updated, and used. Whitelisting techniques can include code signing, digital certificates, known good cryptographic hashes, or trusted full paths and names. Blacklisting, alternatively, blocks known bad software from being downloaded and installed.

  • Host-based firewalls—Defense in depth dictates that the company should consider not just enterprise firewalls but also host-based firewalls.

  • Configuration lockdown—Not just anyone should have the ability to make changes to equipment or hardware. Configurations controls can be used to prevent unauthorized changes.

  • Antivirus—This is the most commonly deployed endpoint security product. While it is a needed component, antivirus has become much less effective over the last several years.

One basic starting point is to implement the principle of least privilege. This concept can also be applied to each logical asset: each computer, system component or process should have the least authority necessary to perform its duties.


A baseline can be described as a standard of security. Baselines are usually mapped to industry standards. As an example, an organization might specify that all computer systems be certified by Common Criteria to an Evaluation Assurance Level (EAL) 3. Another example of baselining can be seen in NIST 800-53. NIST 800-53 describes a tailored baseline as a starting point for determining the needed level of security as seen in Figure 2.4.

  • IT structure analysis (survey)—Includes analysis of technical, operation, and physical aspects of the organization, division, or group.

  • Assessment of protection needs—Determination of the needed level of protection. This activity can be quantitative or qualitative.

  • Selection of actions—Determination of what specific controls need to be implemented.

  • Running comparison of nominal and actual—Periodic review of activities and actions to measure the change between what was previously occurring and what is currently occurring.

Figure 2.4

Figure 2.4 NIST 800-53 Scoping and Baselining Controls.

NIST 800-53 specifies scoping or tailoring activities and categorizes information based on impact.

  • Low impact

  • Moderate impact

  • High impact

Scoping or tailoring is the act of adding or removing controls as needed to get the right level of protection. Obviously, adding controls will increase cost and generally increase system security, whereas removing controls reduces costs but can expose the system to unnecessary threats. Therefore due care must be used to determine the proper level of controls. Scoping and tailoring activities should be well documented with appropriate justification. In some cases, information and information systems must be protected regardless of the cost, because of laws that may govern certain industries.

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