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When the "Read all properties" permission of a user object is set to be audited in the AD, an event of ID 4662 (An operation was performed on an object) is triggered whenever a property is accessed. This rule detects these events by flagging any non-machine `SubjectUserName` (i.e. another user) which accesses an object of the `User` AD schema class. Advantages of this rule include the detection of insider-enumeration through automated tools such as BloodHound or manually through the usage of the PowerShell ActiveDirectory module. Although this rule qualifies as a medium severity one, this event could be qualified as high/critical one if flagged on non-used canary user-accounts. False positives may include administrators performing the initial configuration of new users.
30 lines
1.4 KiB
YAML
30 lines
1.4 KiB
YAML
title: AD User Enumeration
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id: ab6bffca-beff-4baa-af11-6733f296d57a
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description: Detects access to a domain user from a non-machine account
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status: experimental
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date: 2020/03/30
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author: Maxime Thiebaut (@0xThiebaut)
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references:
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- https://www.specterops.io/assets/resources/an_ace_up_the_sleeve.pdf
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- http://www.stuffithoughtiknew.com/2019/02/detecting-bloodhound.html
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- https://docs.microsoft.com/en-us/windows/win32/adschema/attributes-all # For further investigation of the accessed properties
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tags:
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- attack.discovery
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- attack.t1087
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logsource:
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product: windows
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service: security
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definition: Requires the "Read all properties" permission on the user object to be audited for the "Everyone" principal
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detection:
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selection:
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EventID: 4662
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ObjectType|contains: # Using contains as the data commonly is structured as "%{bf967aba-0de6-11d0-a285-00aa003049e2}"
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- 'bf967aba-0de6-11d0-a285-00aa003049e2' # The user class (https://docs.microsoft.com/en-us/windows/win32/adschema/c-user)
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filter:
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- SubjectUserName|endswith: '$' # Exclude machine accounts
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- SubjectUserName|startswith: 'MSOL_' # https://docs.microsoft.com/en-us/azure/active-directory/hybrid/reference-connect-accounts-permissions#ad-ds-connector-account
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condition: selection and not filter
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falsepositives:
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- Administrators configuring new users.
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level: medium
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