Title: Evaluating the Robustness of Time Series Anomaly and Intrusion Detection Methods against Adversarial Attacks. Abstract: Time series anomaly and intrusion detection are extensively studied in statistics, economics, and computer science. Over the years, numerous methods have been proposed for time series anomaly and intrusion detection using deep learning-based methods. Many of these methods demonstrate state-of-the-art performance on benchmark datasets, giving the false impression that these systems are robust and deployable in practical and industrial scenarios. In this paper, we demonstrate that state-of-the-art anomaly and intrusion detection methods can be easily fooled by adding adversarial perturbations to the sensor data. We use different scoring metrics such as prediction errors, anomaly, and classification scores over several public and private datasets belong to aerospace applications, automobiles, server machines, and cyber-physical systems. We evaluate state-of-the-art deep neural networks (DNNs) and graph neural networks (GNNs) methods, which claim to be robust against anomalies and intrusions, and find their performance can drop to as low as 0\% under adversarial attacks from Fast Gradient Sign Method (FGSM) and Projected Gradient Descent (PGD) methods.  To the best of our knowledge, we are the first to demonstrate the vulnerabilities of anomaly and intrusion detection systems against adversarial attacks. Our code is available here: https://anonymous.4open.science/r/ICLR298