
Beyond DKIM key rotation: understanding email replay attacks
DKIM replay attacks are explained: an attacker resends a genuinely signed message unchanged from their own servers, so DKIM passes and DMARC passes even at p=reject. The post shows how to tell replay from spoofing or a legitimate relay using DMARC rua reports, why rotating a key without removing the old public key from DNS leaves messages replayable, and how Amazon SES (BYODKIM vs Easy DKIM), Route 53 and CloudWatch support detection and response. It ends with an ordered incident-response procedure.
Blue Team & Detection, Cloud & InfraΒ· Published and added 2 Nov 2026
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