Evaluation Assurance Level

EAL1 is applicable where some confidence in correct operation is required, but the threats to security are not viewed as serious. It will be of value where independent assurance is required support the contention that due care has been exercised with respect to the protection of personal or similar information. EAL1 provides an evaluation of the TOE (Target of Evaluation) as made available to the customer, including independent testing against a specification, and an examination of the guidance documentation provided. It is intended that an EAL1 evaluation could be successfully conducted without assistance from the developer of the TOE, and for minimal cost. An evaluation at this level should provide evidence that the TOE functions in a manner consistent with its documentation, and that it provides useful protection against identified threats.

EAL2 requires the cooperation of the developer in terms of the delivery of design information and test results, but should not demand more effort on the part of the developer than is consistent with good commercial practice. As such it should not require a substantially increased investment of cost or time. EAL2 is therefore applicable in those circumstances where developers or users require a low to moderate level of independently assured security in the absence of ready availability of the complete development record. Such a situation may arise when securing legacy systems.

EAL3 permits a conscientious developer to gain maximum assurance from positive security engineering at the design stage without substantial alteration of existing sound development practices. EAL3 is applicable in those circumstances where developers or users require a moderate level of independently assured security, and require a thorough investigation of the TOE and its development without substantial re-engineering.

EAL4 permits a developer to gain maximum assurance from positive security engineering based on good commercial development practices which, though rigorous, do not require substantial specialist knowledge, skills, and other resources. EAL4 is the highest level at which it is likely to be economically feasible to retrofit to an existing product line. EAL4 is therefore applicable in those circumstances where developers or users require a moderate to high level of independently assured security in conventional commodity TOEs and are prepared to incur additional security-specific engineering costs.

Commercial operating systems that provide conventional, user-based security features are typically evaluated at EAL4. Examples with expired Certificate are AIX,[1] HP-UX,[1] Oracle Linux, NetWare, Solaris,[1] SUSE Linux Enterprise Server 9,[1][2] SUSE Linux Enterprise Server 10,[3] Red Hat Enterprise Linux 5,[4][5] Windows 2000 Service Pack 3, Windows 2003,[1][6] Windows XP,[1][6] Windows Vista,[7][8] Windows 7,[1][9] Windows Server 2008 R2,[1][9] z/OS version 2.1 and z/VM version 6.3.[1]

Operating systems that provide multilevel security are evaluated at a minimum of EAL4. Examples with active Certificate include SUSE Linux Enterprise Server 15 (EAL 4+).[10] Examples with expired Certificate are Trusted Solaris, Solaris 10 Release 11/06 Trusted Extensions,[11] an early version of the XTS-400, VMware ESXi version 4.1,[12] 3.5, 4.0, AIX 4.3, AIX 5L, AIX 6, AIX7, Red Hat 6.2 & SUSE Linux Enterprise Server 11 (EAL 4+). vSphere 5.5 Update 2 did not achieve EAL4+ level it was an EAL2+ and certified on June 30, 2015.

EAL5 permits a developer to gain maximum assurance from security engineering based upon rigorous commercial development practices supported by moderate application of specialist security engineering techniques. Such a TOE will probably be designed and developed with the intent of achieving EAL5 assurance. It is likely that the additional costs attributable to the EAL5 requirements, relative to rigorous development without the application of specialized techniques, will not be large. EAL5 is therefore applicable in those circumstances where developers or users require a high level of independently assured security in a planned development and require a rigorous development approach without incurring unreasonable costs attributable to specialist security engineering techniques.

Numerous smart card devices have been evaluated at EAL5, as have multilevel secure devices such as the Tenix Interactive Link. XTS-400 (STOP 6) is a general-purpose operating system which has been evaluated at EAL5 augmented.

LPAR on IBM System z is EAL5 Certified.[13]

EAL6 permits developers to gain high assurance from application of security engineering techniques to a rigorous development environment in order to produce a premium TOE for protecting high-value assets against significant risks. EAL6 is therefore applicable to the development of security TOEs for application in high risk situations where the value of the protected assets justifies the additional costs.

Green Hills Software's INTEGRITY-178B RTOS has been certified to EAL6 augmented.[1]

EAL7 is applicable to the development of security TOEs for application in extremely high risk situations and/or where the high value of the assets justifies the higher costs.

Practical application of EAL7 is currently limited to TOEs with tightly focused security functionality that is amenable to extensive formal analysis. The Tenix Interactive Link Data Diode Device and the Fox-IT Fox Data Diode (one-way data communications device) claimed to have been evaluated at EAL7 augmented (EAL7+).[14]

In 2006, the US Government Accountability Office published a report on Common Criteria evaluations that summarized a range of costs and schedules reported for evaluations performed at levels EAL2 through EAL4.

Range of completion times and costs for Common Criteria evaluations at EAL2 through EAL4.

In the mid to late 1990s, vendors reported spending US$1 million and even US$2.5 million on evaluations comparable to EAL4. There have been no published reports of the cost of the various Microsoft Windows security evaluations.

In some cases, the evaluation may be augmented to include assurance requirements beyond the minimum required for a particular EAL. Officially this is indicated by following the EAL number with the word augmented and usually with a list of codes to indicate the additional requirements. As shorthand, vendors will often simply add a "plus" sign (as in EAL4+) to indicate the augmented requirements.

The Common Criteria standards denote EALs as shown in this article: the prefix "EAL" concatenated with a digit 1 through 7 (Examples: EAL1, EAL3, EAL5). In practice, some countries place a space between the prefix and the digit (EAL 1, EAL 3, EAL 5). The use of a plus sign to indicate augmentation is an informal shorthand used by product vendors (EAL4+ or EAL 4+).