MACsec is a Layer 2 security standard for the confidentiality, integrity, and authenticity of Ethernet frames.

IEEE 802.1AE, usually called MACsec, is the standard for Media Access Control Security on Layer 2. It provides confidentiality, integrity, and source authenticity for Ethernet frames between directly connected network participants. MACsec is not end-to-end application-layer encryption, but rather protects hop-by-hop at the Ethernet level—exactly where lines or transitions between devices are to be secured. In the Automotive Ethernet environment, MACsec becomes relevant when zones, backbones, or external cable segments must be protected against tampering and unauthorized eavesdropping.