  Deep neural networks (DNNs) have achieved state-of-the-art performance in
many tasks but have shown extreme vulnerabilities to attacks generated by
adversarial examples. Many works go with a white-box attack that assumes total
access to the targeted model including its architecture and gradients. A more
realistic assumption is the black-box scenario where an attacker only has
access to the targeted model by querying some input and observing its predicted
class probabilities. Different from most prevalent black-box attacks that make
use of substitute models or gradient estimation, this paper proposes a
gradient-free attack by using a concept of evolutionary art to generate
adversarial examples that iteratively evolves a set of overlapping transparent
shapes. To evaluate the effectiveness of our proposed method, we attack three
state-of-the-art image classification models trained on the CIFAR-10 dataset in
a targeted manner. We conduct a parameter study outlining the impact the number
and type of shapes have on the proposed attack's performance. In comparison to
state-of-the-art black-box attacks, our attack is more effective at generating
adversarial examples and achieves a higher attack success rate on all three
baseline models.
