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: Structurally Tested 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: Methodically Tested and Checked 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: Methodically Designed, Tested and Reviewed 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, Oracle Linux, NetWare, Solaris, SUSE Linux Enterprise Server 9, SUSE Linux Enterprise Server 10, Red Hat Enterprise Linux 5, Windows 2000 Service Pack 3, Windows 2003, Windows XP, Windows Vista, Windows 7, Windows Server 2008 R2, z/OS version 2.1 and z/VM version 6.3. 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+). 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,