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Segregation of Duties

Segregation of duties (SoD) policies allow organizations to define toxic combinations of entitlements, which no one user should possess. The most common business driver for these policies is fraud prevention -- i.e., ensuring that fraud cannot be committed without collusion by at least two people.

An effective SoD policy engine has several components:

  • Policy definitions:

    Define sets of two or more entitlements that should not be held by a single user.

  • Approved exceptions:

    Allow users to be assigned entitlements that violate an SoD rule, but with suitable business approval.

  • Preventive enforcement:

    Change requests that pass through an IAM system should be subject to SoD policy tests. Changes that would trigger an SoD violation should be blocked at request time.

  • Detective enforcement:

    Users and entitlements often exist before the deployment of an IAM system or the definition of a given SoD rule. Users may be assigned entitlements using tools other than the IAM system, therefore bypassing preventive enforcement. In each case, it is important to find and remediate violations after the fact.

An effective SoD policy engine should detect violations even if the policy is stated in terms of roles but the violation is in terms of lower-level entitlements -- or vice-versa.

Consider the following variations, where R1 is a role that consists of entitlements Ea and Eb and R2 is a role that consists of entitlements Ec and Ed, as shown in Figure [link].

figure

    Example of entitlements included in roles

Using this example, we can formulate a variety of SoD policies and identify multiple ways to violate each policy, as follows:

SoD policy

Initial

Requested

Why this is a violation
No Eb + Ec.

Eb

Ec

User has Eb directly, would get Ec.

Eb

Mirror image of the previous situation.

R1

User would get Eb from R1.

Ec

Mirror image of the previous situation.

R2

User has Eb from R1, would get Ec from R2.

R1

Mirror image of the previous situation.

R2

User has Eb directly, would get Ec from R2.

Eb

Mirror image of the previous situation.
No R1 + R2.

R1

R2

Direct violation.

Ec, Ed

User would effectively get R2.

\vdots

Many more permutations...

 

A separate source of complexity is nested groups. i.e., entitlements on most systems are just groups, to which users are assigned and which are assigned access rights. Simple groups contain only accounts, but some systems, such as AD and RAC/F, support nested groups, where the members of a group can include other groups.

Just as nested roles create complexity and cause some SoD policy engines to fail to detect violations, nested groups can also prevent some SoD policy engines from detecting violations.

Hitachi ID Identity Manager includes the most advanced segregation of duties (SoD) engine available. It actually works, whereas competitor product SoD engines can be bypassed where both SoD rules and roles are deployed.

The Identity Manager SoD policy engine supports:

  • Policy definition:
    • An SoD rule is defined as a toxic sets of entitlements.
    • Entitlements that participate in the SoD rule may themselves be roles, login IDs on specified target systems or membership in specific security groups.
    • Users who have at least N of the M SoD entitlements are considered to be in violation.

    This is a very general model. It supports rules such as "No user shall belong to more than 2 of these 30 groups."

  • Approved exceptions:
    • Users may be allowed to violate SoD rules, so long as an authorized person has approved the violation.
    • Access certification is used to periodically renew approved SoD exceptions.

    This is a practical model. It allows organizations to knowingly violate rules where there is a strong business reason to do so and where suitable compensating controls are in place.

  • Proactive enforcement:
    • Identity Manager's SoD policy engine is an integral part of the workflow engine.
    • All change requests that pass through the Identity Manager workflow engine must either:
      1. Satisfy all SoD rules (i.e., violate none); or
      2. Include a request for an approved exception to every violated rule.
    • Requesters -- via the Identity Manager UI, API or automation engine -- simply cannot ask for violations without also asking for an approved exception.

    SoD should be proactive rather than after-the-fact, wherever possible. This is supported by Identity Manager.

  • Reporting on out-of-band and pre-existing violations:
    • There are several ways to bypass the Identity Manager pro-active SoD enforcement engine:
      • Pre-existing conditions, where a user violated the SoD rule before Identity Manager was implemented.
      • Pre-existing conditions, where a user violated the SoD rule before the rule was added to Identity Manager.
      • Out of band changes, made by administrators outside of Identity Manager.
    • In these cases, there is no general way for Identity Manager to know which of the offending entitlements is inappropriate, so it cannot automatically remediate the violating users.
    • Instead, Identity Manager includes reports to identify violating users and help security staff make appropriate remediating changes.

    SoD reporting is the defense of last resort.

  • Deep inspection:

    Roles can be nested into other roles. Groups can include among their members other groups. The result of these two hierarchies is that an SoD policy may be defined at one level of a hierarchy of roles or groups, but a violation may take place at another level of the hierarchy. The Identity Manager SoD policy engine decomposes roles and groups and will always detect policy violations. SoD policy engines in competitor products cannot detect such violations.

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