Systems and methods for detecting nonfunctional endpoint devices

The disclosed computer-implemented method for detecting nonfunctional endpoint devices may include (i) identifying, at a networking device, an endpoint device, (ii) identifying, at the networking device, a behavioral profile of the endpoint device that may include (a) a functional pattern of network behavior of the endpoint device that occurs while the endpoint device is in a functional state and/or (b) a nonfunctional pattern of network behavior of the endpoint device that occurs while the endpoint device is in a nonfunctional state, (iii) passively monitoring, at the networking device, network traffic of the endpoint device, (iv) determining, at the networking device, that the endpoint device is nonfunctional by detecting (a) an absence of the functional pattern in the network traffic and/or (b) a presence of the nonfunctional pattern in the network traffic, and (v) performing a security action. Various other methods, systems, and computer-readable media are also disclosed.