The trusted computing base (TCB) of a computer system is the set of all hardware, firmware, and/or software components that are critical to its security, in the sense that bugs or vulnerabilities occurring inside the TCB might jeopardize the security properties of the entire system. By contrast, parts of a computer system that lie outside the TCB must not be able to misbehave in a way that would leak any more privileges than are granted to them in accordance to the system's security policy.
In the security engineering subspecialty of computer science, a trusted system is one that is relied upon to a specified extent to enforce a specified security policy. This is equivalent to saying that a trusted system is one whose failure would break a security policy.
The Common Criteria for Information Technology Security Evaluation is an international standard for computer security certification. It is currently in version 3.1 revision 5.
In computer security, a covert channel is a type of attack that creates a capability to transfer information objects between processes that are not supposed to be allowed to communicate by the computer security policy. The term, originated in 1973 by Butler Lampson, is defined as channels "not intended for information transfer at all, such as the service program's effect on system load," to distinguish it from legitimate channels that are subjected to access controls by COMPUSEC.
In computing, security-evaluated operating systems have achieved certification from an external security-auditing organization, the most popular evaluations are Common Criteria (CC) and FIPS 140-2.
In computer security, mandatory access control (MAC) refers to a type of access control by which the operating system or database constrains the ability of a subject or initiator to access or generally perform some sort of operation on an object or target. In the case of operating systems, a subject is usually a process or thread; objects are constructs such as files, directories, TCP/UDP ports, shared memory segments, IO devices, etc. Subjects and objects each have a set of security attributes. Whenever a subject attempts to access an object, an authorization rule enforced by the operating system kernel examines these security attributes and decides whether the access can take place. Any operation by any subject on any object is tested against the set of authorization rules to determine if the operation is allowed. A database management system, in its access control mechanism, can also apply mandatory access control; in this case, the objects are tables, views, procedures, etc.
In computer security, discretionary access control (DAC) is a type of access control defined by the Trusted Computer System Evaluation Criteria (TCSEC) as a means of restricting access to objects based on the identity of subjects and/or groups to which they belong. The controls are discretionary in the sense that a subject with a certain access permission is capable of passing that permission on to any other subject.
Multilevel security or multiple levels of security (MLS) is the application of a computer system to process information with incompatible classifications, permit access by users with different security clearances and needs-to-know, and prevent users from obtaining access to information for which they lack authorization. There are two contexts for the use of multilevel security.
The Evaluation Assurance Level of an IT product or system is a numerical grade assigned following the completion of a Common Criteria security evaluation, an international standard in effect since 1999. The increasing assurance levels reflect added assurance requirements that must be met to achieve Common Criteria certification. The intent of the higher levels is to provide higher confidence that the system's principal security features are reliably implemented. The EAL level does not measure the security of the system itself, it simply states at what level the system was tested.
In operating systems architecture a reference monitor concept defines a set of design requirements on a reference validation mechanism, which enforces an access control policy over subjects' ability to perform operations on objects on a system. The properties of a reference monitor are captured by the acronym NEAT, which means:
Multiple single-level or multi-security level (MSL) is a means to separate different levels of data by using separate computers or virtual machines for each level. It aims to give some of the benefits of multilevel security without needing special changes to the OS or applications, but at the cost of needing extra hardware.
The XTS-400 is a multilevel secure computer operating system. It is multiuser and multitasking that uses multilevel scheduling in processing data and information. It works in networked environments and supports Gigabit Ethernet and both IPv4 and IPv6.
Solaris Trusted Extensions is a set of security extensions incorporated in the Solaris 10 operating system by Sun Microsystems, featuring a mandatory access control model. It succeeds Trusted Solaris, a family of security-evaluated operating systems based on earlier versions of Solaris.
A Protection Profile (PP) is a document used as part of the certification process according to ISO/IEC 15408 and the Common Criteria (CC). As the generic form of a Security Target (ST), it is typically created by a user or user community and provides an implementation independent specification of information assurance security requirements. A PP is a combination of threats, security objectives, assumptions, security functional requirements (SFRs), security assurance requirements (SARs) and rationales.
A cross-domain solution (CDS) is an integrated information assurance system composed of specialized software, and sometimes hardware, that provides a controlled interface to manually or automatically enable and/or restrict the access or transfer of information between two or more security domains based on a predetermined security policy. CDSs are designed to enforce domain separation and typically include some form of content filtering, which is used to designate information that is unauthorized for transfer between security domains or levels of classification, such as between different military divisions, intelligence agencies, or other operations which depend on the timely sharing of potentially sensitive information.
System high mode, or simply system high, is a security mode of using an automated information system (AIS) that pertains to an environment that contains restricted data that is classified in a hierarchical scheme, such as Top Secret, Secret and Unclassified. System high pertains to the IA features of information processed, and specifically not to the strength or trustworthiness of the system.
A separation kernel is a type of security kernel used to simulate a distributed environment. The concept was introduced by John Rushby in a 1981 paper. Rushby proposed the separation kernel as a solution to the difficulties and problems that had arisen in the development and verification of large, complex security kernels that were intended to "provide multilevel secure operation on general-purpose multi-user systems." According to Rushby, "the task of a separation kernel is to create an environment which is indistinguishable from that provided by a physically distributed system: it must appear as if each regime is a separate, isolated machine and that information can only flow from one machine to another along known external communication lines. One of the properties we must prove of a separation kernel, therefore, is that there are no channels for information flow between regimes other than those explicitly provided."
In information security, a guard is a device or system for allowing computers on otherwise separate networks to communicate, subject to configured constraints. In many respects a guard is like a firewall and guards may have similar functionality to a gateway.
The Controlled Access Protection Profile, also known as CAPP, is a Common Criteria security profile that specifies a set of functional and assurance requirements for information technology products. Software and systems that conform to CAPP standards provide access controls that are capable of enforcing access limitations on individual users and data objects. CAPP-conformant products also provide an audit capability which records the security-relevant events which occur within the system.
Security Controls for Computer Systems, commonly called the Ware report, is a 1970 text by Willis Ware that was foundational in the field of computer security.
