1. A Support Vector Machine (SVM) classifier training device comprising: a computer programmed to train a Support Vector Machine (SVM) one-class classifier using a Radial Basis Function (RBF) kernel to perform security monitoring of a controller area network (CAN) bus employing a message-based communication protocol by operations including: receiving a training set comprising vectors with associated times representing CAN bus messages; calculating a hyperplane curvature parameter γ functionally dependent on message density in time; and training the SVM one-class classifier on the training set using the calculated γ.