  Adversarial perturbations can pose a serious threat for deploying machine
learning systems. Recent works have shown existence of image-agnostic
perturbations that can fool classifiers over most natural images. Existing
methods present optimization approaches that solve for a fooling objective with
an imperceptibility constraint to craft the perturbations. However, for a given
classifier, they generate one perturbation at a time, which is a single
instance from the manifold of adversarial perturbations. Also, in order to
build robust models, it is essential to explore the manifold of adversarial
perturbations. In this paper, we propose for the first time, a generative
approach to model the distribution of adversarial perturbations. The
architecture of the proposed model is inspired from that of GANs and is trained
using fooling and diversity objectives. Our trained generator network attempts
to capture the distribution of adversarial perturbations for a given classifier
and readily generates a wide variety of such perturbations. Our experimental
evaluation demonstrates that perturbations crafted by our model (i) achieve
state-of-the-art fooling rates, (ii) exhibit wide variety and (iii) deliver
excellent cross model generalizability. Our work can be deemed as an important
step in the process of inferring about the complex manifolds of adversarial
perturbations.
