  Machine Learning (ML) has been instrumental in enabling joint transceiver
optimization by merging all physical layer blocks of the end-to-end wireless
communication systems. Although there have been a number of adversarial attacks
on ML-based wireless systems, the existing methods do not provide a
comprehensive view including multi-modality of the source data, common physical
layer components, and wireless domain constraints. This paper proposes Magmaw,
the first black-box attack methodology capable of generating universal
adversarial perturbations for any multimodal signal transmitted over a wireless
channel. We further introduce new objectives for adversarial attacks on
ML-based downstream applications. The resilience of the attack to the existing
widely used defense methods of adversarial training and perturbation signal
subtraction is experimentally verified. For proof-of-concept evaluation, we
build a real-time wireless attack platform using a software-defined radio
system. Experimental results demonstrate that Magmaw causes significant
performance degradation even in the presence of the defense mechanisms.
Surprisingly, Magmaw is also effective against encrypted communication channels
and conventional communications.
