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Application & OT Security · Advanced

Constrained Application Protocol (CoAP)

A lightweight REST-like UDP protocol (RFC 7252) for constrained IoT devices, secured with DTLS or OSCORE.

Definition

CoAP uses UDP port 5683 (5684 with DTLS) and supports methods like GET and PUT plus multicast discovery. Unsecured, internet-exposed CoAP services have been abused for UDP amplification attacks, so access should be restricted and DTLS used.

Example

A sensor network secures CoAP with DTLS and blocks UDP 5683 at the internet edge.

Exam tip

UDP-based, so amplification risk when exposed.

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