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InformationalSplunk security contentSteven Dick

Windows Unusual NTLM Authentication Destinations By Source

The following analytic detects when an unusual number NTLM authentications is attempted by the same source against multiple destinations. This activity generally results when an attacker attempts to brute force,…

Description

The following analytic detects when an unusual number NTLM authentications is attempted by the same source against multiple destinations. This activity generally results when an attacker attempts to brute force, password spray, or otherwise authenticate to a multiple domain joined Windows devices using an NTLM based process/attack. This same activity may also generate a large number of EventID 4776 events as well.

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
ntlm_operational_8004ntlm_operational_8005ntlm_operational_8006

Known benign triggers

  • Vulnerability scanners, print servers, and applications that deal with non-domain joined authentications. Recommend adjusting the upperBound_unique eval for tailoring the correlation to your environment, running with a 24hr search window will smooth out some statistical noise.

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