Today's trend of an increasing number of networked embedded devices pervades many areas. Ranging from home automation, industrial or automotive applications with a large number of different protocols, low resources and often high demands on real-time make it difficult to secure the communication of such systems. A concept of an uncoupled MAC which is able to ensure the authenticity and integrity of communication flows between two network parties can be used. This is in particular of advance for outdated legacy components still participating in the network. In this paper a assessment simulation model of the mechanism behind this technology is described. It outlines the probability of detecting an attack depending on the message authentication overhead. The model considers all control variables and performs measurements based on random data traffic. The results of the statistical analysis state that a high attack detection rate can be obtained even with a small communication overhead.