1. A method comprising: obtaining a plurality of training vectors, each to contain a plurality of keystroke pattern values derived from keystrokes entered by a user; adding a new output node to a neural network, the new output node connected directly to each of a plurality of input nodes by a first weight and connected directly to each of the plurality of input nodes by a second weight; training the first weights connecting the input nodes to the new output node with the plurality of training vectors; and training the second weights connecting the input nodes to the new output node with the plurality of training vectors.