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All information security measures try to address at least one of three goals:
- Protect the confidentiality of data
- Preserve the integrity of data
- Promote the availability of data for authorized use
These goals form the confidentiality, integrity, availability (CIA) triad, the basis of all security programs. Information security professionals who create policies and procedures (often referred to as governance models) must consider each goal when creating a plan to protect a computer system.
The CIA Triad
The CIA triad of confidentiality, integrity, and availability is at the heart of information security. There is continuous debate about extending this classic trio. Other principles such as Accountability have sometimes been proposed for addition – it has been pointed out that issues such as Non-Repudiation do not fit well within the three core concepts.
In 1992 and revised in 2002, the OECD’s Guidelines for the Security of Information Systems and Networks proposed the nine generally accepted principles: Awareness, Responsibility, Response, Ethics, Democracy, Risk Assessment, Security Design and Implementation, Security Management, and Reassessment. Building upon those, in 2004 the NIST’s Engineering Principles for Information Technology Security proposed 33 principles. From each of these derived guidelines and practices.
In 2002, Donn Parker proposed an alternative model for the classic CIA triad that he called the six atomic elements of information. The elements are confidentiality, possession, integrity, authenticity, availability, and utility. The merits of the Parkerian hexad are a subject of debate amongst security professionals.
In 2013, based on a thorough analysis of Information Assurance and Security (IAS) literature, the IAS-octave was proposed as an extension of the CIA-triad. The IAS-octave includes Confidentiality, Integrity, Availability, Accountability, Auditability, Authenticity/Trustworthiness, Non-repudiation and Privacy. The completeness and accuracy of the IAS-octave was evaluated via a series of interviews with IAS academics and experts. The IAS-octave is one of the dimensions of a Reference Model of Information Assurance and Security (RMIAS), which summarizes the IAS knowledge in one all-encompassing model.
Confidentiality – In information security, confidentiality “is the property, that information is not made available or disclosed to unauthorized individuals, entities, or processes” (Excerpt ISO27000).
Confidentiality is roughly equivalent to privacy. Measures undertaken to ensure confidentiality are designed to prevent sensitive information from reaching the wrong people, while making sure that the right people can in fact get it: Access must be restricted to those authorized to view the data in question. It is common, as well, for data to be categorized according to the amount and type of damage that could be done should it fall into unintended hands. More or less stringent measures can then be implemented according to those categories.
Sometimes safeguarding data confidentiality may involve special training for those privy to such documents. Such training would typically include security risks that could threaten this information. Training can help familiarize authorized people with risk factors and how to guard against them. Further aspects of training can include strong passwords and password-related best practices and information about social engineering methods, to prevent them from bending data-handling rules with good intentions and potentially disastrous results.
A good example of methods used to ensure confidentiality is an account number or routing number when banking online. Data encryption is a common method of ensuring confidentiality. User IDs and passwords constitute a standard procedure; two-factor authentication is becoming the norm. Other options include biometric verification and security tokens, key fobs or soft tokens. In addition, users can take precautions to minimize the number of places where the information appears and the number of times it is actually transmitted to complete a required transaction. Extra measures might be taken in the case of extremely sensitive documents, precautions such as storing only on air gapped computers, disconnected storage devices or, for highly sensitive information, in hard copy form only.
Integrity – Data integrity means maintaining and assuring the accuracy and completeness of data over its entire life-cycle. This means that data cannot be modified in an unauthorized or undetected manner. This is not the same thing as referential integrity in databases, although it can be viewed as a special case of consistency as understood in the classic ACID model of transaction processing. Information security systems typically provide message integrity in addition to data confidentiality.
Data must not be changed in transit, and steps must be taken to ensure that data cannot be altered by unauthorized people (for example, in a breach of confidentiality). These measures include file permissions and user access controls. Version control maybe used to prevent erroneous changes or accidental deletion by authorized users becoming a problem. In addition, some means must be in place to detect any changes in data that might occur as a result of non-human-caused events such as an electromagnetic pulse (EMP) or server crash. Some data might include checksums, even cryptographic checksums, for verification of integrity. Backups or redundancies must be available to restore the affected data to its correct state.
Integrity models keep data pure and trustworthy by protecting system data from intentional or accidental changes. Integrity models have three goals:
- Prevent unauthorized users from making modifications to data or programs
- Prevent authorized users from making improper or unauthorized modifications
- Maintain internal and external consistency of data and programs
An example of integrity checks is balancing a batch of transactions to make sure that all the information is present and accurately accounted for.
Availability – For any information system to serve its purpose, the information must be available when it is needed. This means that the computing systems used to store and process the information, the security controls used to protect it, and the communication channels used to access it must be functioning correctly. High availability systems aim to remain available at all times, preventing service disruptions due to power outages, hardware failures, and system upgrades. Ensuring availability also involves preventing denial-of-service attacks, such as a flood of incoming messages to the target system essentially forcing it to shut down.
Availability is best ensured by rigorously maintaining all hardware, performing hardware repairs immediately when needed and maintaining a correctly functioning operating system environment that is free of software conflicts. It’s also important to keep current with all necessary system upgrades. Providing adequate communication bandwidth and preventing the occurrence of bottlenecks are equally important. Redundancy, failover, RAID even high-availability clusters can mitigate serious consequences when hardware issues do occur. Fast and adaptive disaster recovery is essential for the worst case scenarios; that capacity is reliant on the existence of a comprehensive disaster recovery plan (DRP). Safeguards against data loss or interruptions in connections must include unpredictable events such as natural disasters and fire. To prevent data loss from such occurrences, a backup copy may be stored in a geographically-isolated location, perhaps even in a fireproof, waterproof safe. Extra security equipment or software such as firewalls and proxy servers can guard against downtime and unreachable data due to malicious actions such as denial-of-service (DoS) attacks and network intrusions.
Availability models keep data and resources available for authorized use, especially during emergencies or disasters. Information security professionals usually address three common challenges to availability:
- Denial of service (DoS) due to intentional attacks or because of undiscovered flaws in implementation (for example, a program written by a programmer who is unaware of a flaw that could crash the program if a certain unexpected input is encountered)
- Loss of information system capabilities because of natural disasters (fires, floods, storms, or earthquakes) or human actions (bombs or strikes)
- Equipment failures during normal use
Some activities that preserve confidentiality, integrity, and/or availability are granting access only to authorized personnel, applying encryption to information that will be sent over the Internet or stored on digital media, periodically testing computer system security to uncover new vulnerabilities, building software defensively, and developing a disaster recovery plan to ensure that the business can continue to exist in the event of a disaster or loss of access by personnel.
Non-repudiation – In law, non-repudiation implies one’s intention to fulfill their obligations to a contract. It also implies that one party of a transaction cannot deny having received a transaction nor can the other party deny having sent a transaction. Note: This is also regarded as part of Integrity.
It is important to note that while technology such as cryptographic systems can assist in non-repudiation efforts, the concept is at its core a legal concept transcending the realm of technology. It is not, for instance, sufficient to show that the message matches a digital signature signed with the sender’s private key, and thus only the sender could have sent the message and nobody else could have altered it in transit. The alleged sender could in return demonstrate that the digital signature algorithm is vulnerable or flawed, or allege or prove that his signing key has been compromised. The fault for these violations may or may not lie with the sender himself, and such assertions may or may not relieve the sender of liability, but the assertion would invalidate the claim that the signature necessarily proves authenticity and integrity and thus prevents repudiation.
Principle of least privilege
The Department of Defense Trusted Computer System Evaluation Criteria, (DOD-5200.28-STD), or Orange Book, is an accepted standard for computer security. This publication defines least privilege as a principle that “requires that each subject in a system be granted the most restrictive set of privileges (or lowest clearance) needed for the performance of authorized tasks. The application of this principle limits the damage that can result from accident, error, or unauthorized use.”
Most security-related training and documentation will mention the principle of least privilege. Although this principle is relatively easy to understand, it is also one that will greatly improve the security profile of any business that implements it. Simply put, this principle states that all accounts should have the absolute minimum set of privileges that are necessary to complete the current tasks and nothing more. This principle applies not only to users, but also for computers and the services that run on them.
Following such a principle not only helps protect against malicious attackers and malware, but also improves the security profile of a company by forcing technology professionals to do extensive research to determine what access privileges are needed by users, computers, and applications. Understanding this information provides insight as to what processes or settings may be insecure and require more protection, and therefore is an essential step to any successful security initiative.
For example, according to the principle of least privilege a person who has the role of domain administrator should only use an account that has the domain admin level privilege when performing tasks that require that level of access. Otherwise, when not performing tasks that require a higher level privilege, an administrator should use an account with standard access rights. Such a practice would reduce security threats that originate from human error and reduce the amount of damage done should an administrative workstation be infected by malware.
Defense in Depth
In the information security world, defense in depth requires layering security devices in a series that protects, detects, and responds to attacks on systems. For example, a typical Internet-attached network designed with security in mind includes routers, firewalls, and intrusion detection systems (IDS) to protect the network from would-be intruders; employs traffic analyzers and real-time human monitors who watch for anomalies as the network is being used to detect any breach in the layers of protection; and relies on automated mechanisms to turn off access or remove the system from the network in response to the detection of an intruder.
Finally, the security of each of these mechanisms must be thoroughly tested before deployment to ensure that the integrated system is suitable for normal operations. After all, a chain is only as good as its weakest link.
The idea behind the defense in depth approach is to defend a system against any particular attack using several independent methods. It is a layering tactic, conceived by the National Security Agency (NSA) as a comprehensive approach to information and electronic security.
Defense in depth is originally a military strategy that seeks to delay rather than prevent the advance of an attacker by yielding space to buy time. The placement of protection mechanisms, procedures and policies is intended to increase the dependability of an IT system, where multiple layers of defense prevent espionage and direct attacks against critical systems. In terms of computer network defense, defense in depth measures should not only prevent security breaches but also buy an organization time to detect and respond to an attack and so reduce and mitigate the consequences of a breach.
