InformationLimit guest user permissions.
Limiting guest access ensures that guest accounts do not have permission for certain directory tasks, such as enumerating users, groups or other directory resources, and cannot be assigned to administrative roles in your directory. Guest access has three levels of restriction.
Guest users have the same access as members (most inclusive),
Guest users have limited access to properties and memberships of directory objects (default value),
Guest user access is restricted to properties and memberships of their own directory objects (most restrictive).
The recommended option is the 3rd, most restrictive: 'Guest user access is restricted to their own directory object'.
This may create additional requests for permissions to access resources that administrators will need to approve.
NOTE: Nessus has not performed this check. Please review the benchmark to ensure target compliance.
SolutionFrom Azure Portal
From Azure Home select the Portal Menu
Select Azure Active Directory
Then External Identities
Select External collaboration settings
Under Guest user access, change Guest user access restrictions to be Guest user access is restricted to properties and memberships of their own directory objects
From a Powershell session enter Set-AzureADMSAuthorizationPolicy -GuestUserRoleId '2af84b1e-32c8-42b7-82bc-daa82404023b'
Check that the setting was applied by entering Get-AzureADMSAuthorizationPolicy
Make certain that the GuestUserRoleId is equal to the earlier entered value of 2af84b1e-32c8-42b7-82bc-daa82404023b.
By default, Guest user access restrictions is set to Guest user access is restricted to properties and memberships of their own directory objects.
Category: ACCESS CONTROL, AUDIT AND ACCOUNTABILITY, MEDIA PROTECTION, RISK ASSESSMENT
References: 800-53|AC-2, 800-53|AC-2(1), 800-53|AC-3, 800-53|AC-5, 800-53|AC-6, 800-53|AC-6(1), 800-53|AC-6(7), 800-53|AU-9(4), 800-53|MP-2, 800-53|RA-2, CSCv7|14.6
Control ID: 450eee86b6f0827f85f5a3562031bb26f3a0b5eb81433cc85eeb87fd5df5975f