Уровни обеспечения Common Criteria: оценка и сертификация ИТ-систем.

Numerical grade assigned following Common Criteria
The Evaluation Assurance Level (EAL1 through EAL7) 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. To achieve a particular EAL, the computer system must meet specific assurance requirements. Most of these requirements involve design documentation, design analysis, functional testing, or penetration testing. The higher EALs involve more detailed documentation, analysis, and testing than the lower ones. Achieving a higher EAL certification generally costs more money and takes more time than achieving a lower one. The EAL number assigned to a certified system indicates that the system completed all requirements for that level. Although every product and system must fulfill the same assurance requirements to achieve a particular level, they do not have to fulfill the same functional requirements. The functional features for each certified product are established in the Security Target document tailored for that product's evaluation. Therefore, a product with a higher EAL is not necessarily "more secure" in a particular application than one with a lower EAL, since they may have very different lists of functional features in their Security Targets. A product's fitness for a particular security application depends on how well the features listed in the product's Security Target fulfill the application's security requirements. If the Security Targets for two products both contain the necessary security features, then the higher EAL should indicate the more trustworthy product for that application.

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, HP UX, SUSE Linux Enterprise Server 10, Red Hat Enterprise Linux 5, Windows 2000 Service Pack 3, Windows 2003, Windows XP,
Windows 7, Windows Server 2008 R2, Examples with expired Certificate are Trusted Solaris, Solaris 10 Release 11/06 Trusted Extensions, an early version of the XTS 400, VMware ESXi version 4.1, 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.

Technically speaking, a higher EAL means nothing more, or less, than that the evaluation completed a more stringent set of quality assurance requirements. It is often assumed that a system that achieves a higher EAL will provide its security features more reliably (and the required third party analysis and testing performed by security experts is reasonable evidence in this direction), but there is little or no published evidence to support that assumption.

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. 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+).