  Transfer adversarial attacks raise critical security concerns in real-world,
black-box scenarios. However, the actual progress of this field is difficult to
assess due to two common limitations in existing evaluations. First, different
methods are often not systematically and fairly evaluated in a one-to-one
comparison. Second, only transferability is evaluated but another key attack
property, stealthiness, is largely overlooked. In this work, we design good
practices to address these limitations, and we present the first comprehensive
evaluation of transfer attacks, covering 23 representative attacks against 9
defenses on ImageNet. In particular, we propose to categorize existing attacks
into five categories, which enables our systematic category-wise analyses.
These analyses lead to new findings that even challenge existing knowledge and
also help determine the optimal attack hyperparameters for our attack-wise
comprehensive evaluation. We also pay particular attention to stealthiness, by
adopting diverse imperceptibility metrics and looking into new, finer-grained
characteristics. Overall, our new insights into transferability and
stealthiness lead to actionable good practices for future evaluations.
