This paper evaluates the performance of long short-term memory recurrent neural networks (LSTM-RNN) on classifying intrusion detection data. LSTM networks can learn memory and can therefore model data as a time series. LSTM is trained and tested on a processed version of the KDDCup99 dataset. A variety of suitable performance measures are discussed and applied. Our LSTM network structure and parameters are experimentally obtained within a series of experiments presented. Results finally show that LSTM is able to learn all attack classes hidden in the training data. Furthermore we learn that the receiver operating characteristic (ROC) curve and the corresponding area-under-the-curve (AUC) value are well suited for selecting well performing networks.