  As deep neural networks (DNNs) have been integrated into critical systems,
several methods to attack these systems have been developed. These adversarial
attacks make imperceptible modifications to an image that fool DNN classifiers.
We present an adaptive JPEG encoder which defends against many of these
attacks. Experimentally, we show that our method produces images with high
visual quality while greatly reducing the potency of state-of-the-art attacks.
Our algorithm requires only a modest increase in encoding time, produces a
compressed image which can be decompressed by an off-the-shelf JPEG decoder,
and classified by an unmodified classifier
