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Event ID 4963: IPsec dropped an inbound clear text packet that should have been secured

Windows Event ID Lookup: What Windows event IDs mean: 4625, 4624, 4740, 6008, 41, 7045, 1102 and 3,000 more, with Windows' own message text, the fields and what to check.

Look up a Windows event ID from Event Viewer, a SIEM alert or a log export: what it means, the fields it records, and what to check. Many IDs are used by more than one source (event 41 is both a Kernel-Power crash and a boot error), so every definition is shown, the one people usually mean first. The message text is Windows' own, read from the event providers of Windows 10.0.26200.0, 2026-10-28; the notes are ours, based on Microsoft's security auditing reference.

Try: 4625, 4624, 4740, 6008, 41, 1074, 7045, 1102, 4104, 1149

IPsec dropped an inbound clear text packet that should have been secured.

Event 4963
Security-Auditing
Security log
Audit
Message and fields (as Event Viewer shows them) 
IPsec dropped an inbound clear text packet that should have been secured. If the remote computer is configured with a Request Outbound IPsec policy, this might be benign and expected.  This can also be caused by the remote computer changing its IPsec policy without informing this computer. This could also be a spoofing attack attempt.

Remote Network Address:	…
Inbound SA SPI:		…