CAE: Contextual auto-encoder for multivariate time-series anomaly detection in air transportation

The Automatic Dependent Surveillance-Broadcast protocol is one of the latest compulsory advances in air surveillance. While it supports the tracking of the ever-growing number of aircraft in the air, it also introduces cybersecurity issues that must be mitigated e.g., false data injection attacks where an attacker emits fake surveillance information. The recent data sources and tools available to obtain flight tracking records allow the researchers to create datasets and develop Machine Learning models capable of detecting such anomalies in En-Route trajectories. In this context, we propose a novel multivariate anomaly detection model called Contextual Auto-Encoder (CAE). It uses the baseline of a regular LSTM-based auto encoder but with several decoders, each getting data of a specific flight phase (e.g. climbing, cruising or descending) during its training. To illustrate the CAE's efficiency, an evaluation dataset was created using real-life anomalies as well as realistically crafted trajectory modifications, with which the CAE as well as three anomaly detection models from the literature were evaluated. Results show that the CAE achieves better results in both accuracy and speed of detection. The dataset, the models implementations and the evaluation results are available in an online repository, thereby enabling replicability and facilitating future experiments. (c) 2022 Elsevier Ltd. All rights reserved.