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Windows Account Discovery With NetUser PreauthNotRequire

Author
Teoderick Contreras, Splunk
Source
upstream

The following analytic detects the execution of the PowerView PowerShell cmdlet Get-NetUser with the -PreauthNotRequire parameter, leveraging Event ID 4104. This method identifies attempts to query Active Directory user accounts that do not require Kerberos preauthentication. Monitoring this activity is crucial as it can indicate reconnaissance efforts by an attacker to identify potentially vulnerable accounts. If confirmed malicious, this behavior could lead to further exploitation, such as unauthorized access or privilege escalation within the network.

MITRE ATT&CK coverage

TacticTechniques
DiscoveryT1087 Account Discovery

Event coverage

ProviderEvent IDTitle
PowerShell4104Creating Scriptblock text (MessageNumber of MessageTotal).

Stages and Predicates

Stage 1: search

search EventCode=4104 ScriptBlockText="*-PreauthNotRequire*" ScriptBlockText="*Get-NetUser*"

Stage 2: fillnull

fillnull

Stage 3: stats

stats BY dest, signature, signature_id, user_id, vendor_product, EventID, Guid, Opcode, Name, Path, ProcessID, ScriptBlockId, ScriptBlockText

Stage 4: search

search

Stage 5: search

search

Stage 6: search

search `macro`

Indicators

Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.

FieldKindValues
EventCodeeq
  • 4104 corpus 108 (splunk 108)
ScriptBlockTexteq
  • "*-PreauthNotRequire*"
  • "*Get-NetUser*" corpus 3 (splunk 3)

Neighbors

Broader alternatives (more inclusive than this rule)

These rules match a superset of what this rule catches. They cover the same events plus more. Use them if you want wider coverage and can absorb more false positives.