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InformationalSplunk security contentMauricio Velazco +1

Windows Unusual Count Of Users Failed To Authenticate Using NTLM

The following analytic identifies a source endpoint failing to authenticate multiple valid users using the NTLM protocol, potentially indicating a Password Spraying attack. It leverages Event 4776 from Domain…

Description

The following analytic identifies a source endpoint failing to authenticate multiple valid users using the NTLM protocol, potentially indicating a Password Spraying attack. It leverages Event 4776 from Domain Controllers, calculating the standard deviation for each host and applying the 3-sigma rule to detect anomalies. This activity is significant as it may represent an adversary attempting to gain initial access or elevate privileges. If confirmed malicious, the attacker could compromise multiple accounts, leading to unauthorized access and potential lateral movement within the network.

Detection logic

Detection requirements

Platform
ContainersESXiIaaSIdentity ProviderLinuxmacOSNetwork DevicesOffice SuiteSaaSWindows

The rule states no platform. This is derived from the ATT&CK technique it maps to.

Log source category
windows_event_log_security_4776

Known benign triggers

  • A host failing to authenticate with multiple valid domain users is not a common behavior for legitimate systems. Possible false positive scenarios include but are not limited to vulnerability scanners and missconfigured systems. If this detection triggers on a host other than a Domain Controller, the behavior could represent a password spraying attack against the host's local accounts.

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