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Embedded devices are omnipresent in modern networks including the ones operating inside critical environments. However, due to their constrained nature, novel mechanisms are required to provide external, and non-intrusive anomaly detection. Among such approaches, one that has gained traction is based on the analysis of the electromagnetic (EM) signals that get emanated during a device's operation. However, one of the most neglected challenges of this approach is the requirement for manually gathering and fingerprinting the signals that correspond to each execution path of the software/firmware. Indeed, even simple programs are comprised of hundreds if not thousands of branches thus, making the fingerprinting stage an extremely time-consuming process that involves the manual labor of a human specialist. To address this issue, we propose a framework for generating synthetic EM signals directly from the machine code. The synthetic signals can be used to train a Machine Learning based (ML) system for anomaly detection. The main advantage of the proposed approach is that it completely removes the need for an elaborate and error-prone fingerprinting stage, thus, dramatically increasing the scalability of the corresponding protection mechanisms. The experimental evaluations indicate that our method provides high detection accuracy (above 90% AUC score) when employed for the detection of injection attacks. Moreover, the proposed methodology inflicts only a small penalty (-1.3%) in accuracy for the detection of the injection of as little as four malicious instructions when compared to the same methods if real signals were to be used.