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HighSigmaHQSwachchhanda Shrawan Poudel (Nextron Systems)

NTLM Hash Leak Via Curl NTLM Authentication

Detects the use of curl with NTLM authentication and empty credentials (-u :), which can be abused to leak the currently logged-in user's NTLMv2 challenge-response to an attacker-controlled server, enabling offline…

Description

Detects the use of curl with NTLM authentication and empty credentials (-u :), which can be abused to leak the currently logged-in user's NTLMv2 challenge-response to an attacker-controlled server, enabling offline cracking or relay attacks. When no credentials are provided, the Microsoft-shipped curl passes a NULL identity to Windows SSPI, which automatically falls back to the current user's logon session credentials stored in LSASS — without requiring a plaintext password. This behavior is exclusive to the curl binary shipped by Microsoft (available since Windows 10 / Windows Server 2019), which is built with SSPI support.

Detection logic

Detection requirements

Platform
Windows

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

Log source product
windows
Log source category
process_creation

Known benign triggers

  • Should be very rare as it's not widely known or used, but could occur in legitimate use cases where curl is used with NTLM authentication and empty credentials, such as in certain scripts or automation tasks.

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