1. An apparatus, comprising: a probe configured to capture side-channel information relating to an operation status of a target device, the probe in a permanently fixed position relative to the target device during a life span of anomaly detection on the target device; a fixture, configured to fixedly hold the probe such that the probe is in a permanently fixed position relative to the target device; a processor, communicatively coupled to the probe, configured to: process the side-channel information to extract a first characteristic of the side-channel information, retrieve previously-stored reference side-channel information having a second characteristic and representing a normal activity of the target device, compare the first characteristic with the second characteristic to determine an anomaly of the target device, and send to a user interface an alert indicative of the anomaly based on the first characteristic and the second characteristic.