# Constrained Concealment Attacks against Reconstruction-based Anomaly Detectors in Industrial Control Systems

## TL;DR

This paper introduces novel constrained concealment attacks on reconstruction-based anomaly detectors in industrial control systems, demonstrating significant reduction in detection recall and transferability across detector types, including real-time implementation.

## Contribution

It proposes two new attack methods exploiting physical constraints, showing their effectiveness and transferability against various anomaly detectors in water distribution systems.

## Key findings

- Replay attacks are less effective when manipulating less than 95% of features.
- Proposed attacks significantly reduce detection recall, e.g., from 0.68 to 0.12.
- Attacks are transferable across different detector architectures.

## Abstract

Recently, reconstruction-based anomaly detection was proposed as an effective technique to detect attacks in dynamic industrial control networks. Unlike classical network anomaly detectors that observe the network traffic, reconstruction-based detectors operate on the measured sensor data, leveraging physical process models learned a priori. In this work, we investigate different approaches to evade prior-work reconstruction-based anomaly detectors by manipulating sensor data so that the attack is concealed. We find that replay attacks (commonly assumed to be very strong) show bad performance (i.e., increasing the number of alarms) if the attacker is constrained to manipulate less than 95% of all features in the system, as hidden correlations between the features are not replicated well. To address this, we propose two novel attacks that manipulate a subset of the sensor readings, leveraging learned physical constraints of the system. Our attacks feature two different attacker models: A white box attacker, which uses an optimization approach with a detection oracle, and a black box attacker, which uses an autoencoder to translate anomalous data into normal data. We evaluate our implementation on two different datasets from the water distribution domain, showing that the detector's Recall drops from 0.68 to 0.12 by manipulating 4 sensors out of 82 in WADI dataset. In addition, we show that our black box attacks are transferable to different detectors: They work against autoencoder-, LSTM-, and CNN-based detectors. Finally, we implement and demonstrate our attacks on a real industrial testbed to demonstrate their feasibility in real-time.