Detectionhightest

NetNTLM Downgrade Attack - Registry

Detects NetNTLM downgrade attack

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Florian Roth (Nextron Systems), wagga, Nasreddine Bencherchali (Nextron Systems)Created Tue Mar 20Updated Tue Dec 03d67572a0-e2ec-45d6-b8db-c100d14b8ef2windows

Log Source

WindowsRegistry Event

ProductWindows← raw: windows

CategoryRegistry Event← raw: registry_event

Events for Windows Registry modifications including key creation, modification, and deletion.

Detection Logic

detection:
    selection_regkey:
        TargetObject|contains|all:
            - 'SYSTEM\'
            - 'ControlSet'
            - '\Control\Lsa'
    selection_value_lmcompatibilitylevel:
        TargetObject|endswith: '\lmcompatibilitylevel'
        Details:
            - 'DWORD (0x00000000)'
            - 'DWORD (0x00000001)'
            - 'DWORD (0x00000002)'
    selection_value_ntlmminclientsec:
        TargetObject|endswith: '\NtlmMinClientSec'
        Details:
            - 'DWORD (0x00000000)' # No Security
            - 'DWORD (0x00000010)' # Only Integrity
            - 'DWORD (0x00000020)' # Only confidentiality
            - 'DWORD (0x00000030)' # Both Integrity and confidentiality
    selection_value_restrictsendingntlmtraffic:
        # Note: The obvious values with issues are 0x00000000 (allow all) and 0x00000001 (audit).
        # 0x00000002 can be secure but only if "ClientAllowedNTLMServers" is properly configured
        # Hence all values should be monitored and investigated
        TargetObject|endswith: '\RestrictSendingNTLMTraffic'
    condition: selection_regkey and 1 of selection_value_*