Orange-book-small

Trusted Computer System Evaluation Criteria (TCSEC) is a US Gov.  DoD standard that sets basic requirements for assessing the effectiveness of computer security controls built into a computer system. The TCSEC was used to evaluate, classify and select computer systems being considered for the processing, storage and retrieval of sensitive or classified information.

TCSEC (Trusted Computer Security Evaluation Criteria – aka Orange Book)

ITSEC (Information Technology Security Evaluation Criteria)

ITSEC / TCSEC

DESCRIPTION

TCSEC / ITSEC (F+E)

ITSEC / (E) EAL
F =

EAL =

 Functionality

Eval Assurance Level

(Highest)

F6-10 / EAL7

F10
  • Networks with high demands on Integrity and Confidentiality.

F9
  • Systems that provide high Confidentiality (like crypto devices).

F8
  • Systems that provide data Integrity during communication.

F7
  • Systems that provide high Availability.

F6
  • Systems that provide high Integrity.

EAL 7
  • Formally verified DESIGN and TESTED.

A = VERIFIED PROTECTION

A1 / F5 + E6
  • Top level security, systems designed to handle TS data.
  • Every step is formally DOCUMENTED and VERIFIED.

o         Classification: Capable of handling TS information.

o         (Trusted Distribution) – Delivered and installed in a secure manner.

o         Covert channels addressed – formally tested and documented.
EAL 6
  • Semi-formally verified design and tested.

B = MADATORY PROTECTION

B3 / F5 + E5
  • Uses Security Labels of B1 and B2, based on Bell-LaPadula.
  • Secure Domains:

o         Classification: Supports sufficient security to house classified data.

o         (Trusted Recovery) – Secure state must be addressed during initial boot process.

o         Covert timing channels addressed – for processing trasactions.

o         Security Admin functions must be clearly identified by System.

o         Requirement for Security Domains.

o         Very difficult to successfully attack and provide sufficient secure controls for very sensitive or Secret data.

o         Compartmented Securiy-Mode of Operation in most cases.

EAL 5
  • Semi-formally designed and tested.

B2 / F4 + E4

  • Uses Security Labels for Data and system design, (including storage devices), based on Bell-LaPadula.
  • Structured:

o         Classification: Supports sufficient security to house classified data.

o         (Trusted Facility Management) required

o         Covert storage channels addressed – for data and/or storage devices.

o         Requires SEPARATE Operator and Administrator ROLES.

o         Change Control is required.

EAL 4
  • Methodically designed, tested, and reviewed.

B1 / F3 + E3
  • Uses Security Labels for Data only, based on Bell-LaPadula.
  • Labeled:

o         Classification: Supports sufficient security to house classified data.

o         Grants access by matching subject and object labels and comparing their permission compatibility.

EAL 3
  • Methodically tested and checked.

C = DISCRETIONARY PROTECTION

C2 / F2 + E2
  • Based on individuals and groups, separates users and information.
  • Controlled Access Protection:

o         Enforce strict logon procedures.

o         Media cleansing.

o         Auditing mechanisms.

o         OBJECT REUSE.

EAL 2
  • Structurally tested.

C1 / F1 + E1

  • Based on individuals and groups, separates users and information.
  • Discretionary Secure Protection:
  • Provide only weak protection mechanisms – NO true individual accountability.

EAL 1
  • Functionally tested.

D = MINIMAL SECURITY

D / E0

(Lowest)
  • Reserved for systems that have been evaluated but failed to meet security criteria.

EAL 0
  • Inadequate assurance.
  • TCSEC was developed by the NCSC (National Computer Security Center)
  • TCSEC’s goal was to provide standard methodology for measuring the amount of trust you can place in a system, produce standards as to what security features for manufacturers to include when developing new commercial products, and to provide government user personnel with a basis for the specific security requirements they were demanding when purchasing products.
  • ITSEC (Information Technology Security Evaluation Criteria) was written to address integrity and availability which the Orange Book did not address.