Mitigating NTLM Relay Attacks by Default

[Windows Security]

Introduction In February 2024, we released an update to Exchange Server which contained a security improvement referenced by CVE-2024-21410 that enabled Extended Protection for Authentication (EPA) by default for new and existing installs of Exchange 2019. While we’re currently unaware of any active threat campaigns involving NTLM relaying attacks against Exchange, we have observed threat actors exploiting this vector in the past.

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