Jonhnathan
114 lines
4.9 KiB
TOML
114 lines
4.9 KiB
TOML
[metadata]
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creation_date = "2022/02/24"
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maturity = "production"
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updated_date = "2022/06/03"
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[rule]
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author = ["Elastic"]
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description = """
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Identifies a modification on the dsHeuristics attribute on the bit that holds the configuration of groups excluded from
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the SDProp process. The SDProp compares the permissions on protected objects with those defined on the AdminSDHolder
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object. If the permissions on any of the protected accounts and groups do not match, the permissions on the protected
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accounts and groups are reset to match those of the domain's AdminSDHolder object, meaning that groups excluded will
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remain unchanged. Attackers can abuse this misconfiguration to maintain long-term access to privileged accounts in these
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groups.
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"""
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from = "now-9m"
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index = ["winlogbeat-*", "logs-system.*"]
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language = "eql"
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license = "Elastic License v2"
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name = "AdminSDHolder SDProp Exclusion Added"
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note = """## Triage and analysis
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### Investigating AdminSDHolder SDProp Exclusion Added
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The SDProp process compares the permissions on protected objects with those defined on the AdminSDHolder object. If the
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permissions on any of the protected accounts and groups do not match, it resets the permissions on the protected
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accounts and groups to match those defined in the domain AdminSDHolder object.
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The dSHeuristics is a Unicode string attribute, in which each character in the string represents a heuristic that is
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used to determine the behavior of Active Directory.
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Administrators can use the dSHeuristics attribute to exclude privilege groups from the SDProp process by setting the
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16th bit (dwAdminSDExMask) of the string to a certain value, which represents the group(s):
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* For example, to exclude the Account Operators group, an administrator would modify the string, so the 16th character
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is set to 1 (i.e., 0000000001000001).
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The usage of this exclusion can leave the accounts unprotected and facilitate the misconfiguration of privileges for the
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excluded groups, enabling attackers to add accounts to these groups to maintain long-term persistence with high
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privileges.
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This rule matches changes of the dsHeuristics object where the 16th bit is set to a value other than zero.
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#### Possible investigation steps
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- Identify the user account that performed the action and whether it should perform this kind of action.
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- Contact the account and system owners and confirm whether they are aware of this activity.
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- Investigate other alerts associated with the user/host during the past 48 hours.
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- Check the value assigned to the 16th bit of the string on the `winlog.event_data.AttributeValue` field:
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- Account Operators eq 1
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- Server Operators eq 2
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- Print Operators eq 4
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- Backup Operators eq 8
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The field value can range from 0 to f (15). If more than one group is specified, the values will be summed together;
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for example, Backup Operators and Print Operators will set the `c` value on the bit.
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### False positive analysis
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- While this modification can be done legitimately, it is not a best practice. Any potential benign true positive (B-TP)
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should be mapped and reviewed by the security team for alternatives as this weakens the security of the privileged group.
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### Response and remediation
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- The change can be reverted by setting the dwAdminSDExMask (16th bit) to 0 in dSHeuristics.
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- Using the incident response data, update logging and audit policies to improve the mean time to detect (MTTD) and the
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mean time to respond (MTTR).
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## Config
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The 'Audit Directory Service Changes' logging policy must be configured for (Success).
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Steps to implement the logging policy with Advanced Audit Configuration:
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```
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Computer Configuration >
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Policies >
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Windows Settings >
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Security Settings >
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Advanced Audit Policies Configuration >
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Audit Policies >
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DS Access >
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Audit Directory Service Changes (Success)
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```
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If enabling an EQL rule on a non-elastic-agent index (such as beats) for versions <8.2, events will not define `event.ingested` and default fallback for EQL rules was not added until 8.2, so you will need to add a custom pipeline to populate `event.ingested` to @timestamp for this rule to work.
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"""
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references = [
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"https://www.cert.ssi.gouv.fr/uploads/guide-ad.html#dsheuristics_bad",
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"https://petri.com/active-directory-security-understanding-adminsdholder-object",
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]
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risk_score = 73
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rule_id = "61d29caf-6c15-4d1e-9ccb-7ad12ccc0bc7"
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severity = "high"
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tags = ["Elastic", "Host", "Windows", "Threat Detection", "Persistence", "Active Directory"]
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timestamp_override = "event.ingested"
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type = "eql"
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query = '''
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any where event.action == "Directory Service Changes" and
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event.code == "5136" and
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winlog.event_data.AttributeLDAPDisplayName : "dSHeuristics" and
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length(winlog.event_data.AttributeValue) > 15 and
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winlog.event_data.AttributeValue regex~ "[0-9]{15}([1-9a-f]).*"
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'''
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[[rule.threat]]
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framework = "MITRE ATT&CK"
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[rule.threat.tactic]
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id = "TA0003"
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name = "Persistence"
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reference = "https://attack.mitre.org/tactics/TA0003/"
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