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Constrained Adversarial Perturbation

Virendra Nishad, Bhaskar Mukhoty, Hilal AlQuabeh, Sandeep K. Shukla, Sayak Ray Chowdhury

TL;DR

This work introduces CAPX, a constrained universal perturbation method that enforces domain-specific feature constraints via an augmented Lagrangian min–max optimization, yielding perturbations with high attack success rates and substantially reduced runtimes across finance, IT networks, healthcare, and cyber-physical systems. The framework supports extensions to CAPx for individual perturbations and includes a data-driven procedure to learn feature constraints from normal data, improving applicability in domains with structured inputs. Empirical results show CAPX outperforms baselines like UAP and ConAML in both efficacy and efficiency, while CAPx demonstrates competitive performance for input-specific attacks. The findings underscore the need for robustness guarantees and defense strategies that account for domain constraints in adversarial settings.

Abstract

Deep neural networks have achieved remarkable success in a wide range of classification tasks. However, they remain highly susceptible to adversarial examples - inputs that are subtly perturbed to induce misclassification while appearing unchanged to humans. Among various attack strategies, Universal Adversarial Perturbations (UAPs) have emerged as a powerful tool for both stress testing model robustness and facilitating scalable adversarial training. Despite their effectiveness, most existing UAP methods neglect domain specific constraints that govern feature relationships. Violating such constraints, such as debt to income ratios in credit scoring or packet flow invariants in network communication, can render adversarial examples implausible or easily detectable, thereby limiting their real world applicability. In this work, we advance universal adversarial attacks to constrained feature spaces by formulating an augmented Lagrangian based min max optimization problem that enforces multiple, potentially complex constraints of varying importance. We propose Constrained Adversarial Perturbation (CAP), an efficient algorithm that solves this problem using a gradient based alternating optimization strategy. We evaluate CAP across diverse domains including finance, IT networks, and cyber physical systems, and demonstrate that it achieves higher attack success rates while significantly reducing runtime compared to existing baselines. Our approach also generalizes seamlessly to individual adversarial perturbations, where we observe similar strong performance gains. Finally, we introduce a principled procedure for learning feature constraints directly from data, enabling broad applicability across domains with structured input spaces.

Constrained Adversarial Perturbation

TL;DR

This work introduces CAPX, a constrained universal perturbation method that enforces domain-specific feature constraints via an augmented Lagrangian min–max optimization, yielding perturbations with high attack success rates and substantially reduced runtimes across finance, IT networks, healthcare, and cyber-physical systems. The framework supports extensions to CAPx for individual perturbations and includes a data-driven procedure to learn feature constraints from normal data, improving applicability in domains with structured inputs. Empirical results show CAPX outperforms baselines like UAP and ConAML in both efficacy and efficiency, while CAPx demonstrates competitive performance for input-specific attacks. The findings underscore the need for robustness guarantees and defense strategies that account for domain constraints in adversarial settings.

Abstract

Deep neural networks have achieved remarkable success in a wide range of classification tasks. However, they remain highly susceptible to adversarial examples - inputs that are subtly perturbed to induce misclassification while appearing unchanged to humans. Among various attack strategies, Universal Adversarial Perturbations (UAPs) have emerged as a powerful tool for both stress testing model robustness and facilitating scalable adversarial training. Despite their effectiveness, most existing UAP methods neglect domain specific constraints that govern feature relationships. Violating such constraints, such as debt to income ratios in credit scoring or packet flow invariants in network communication, can render adversarial examples implausible or easily detectable, thereby limiting their real world applicability. In this work, we advance universal adversarial attacks to constrained feature spaces by formulating an augmented Lagrangian based min max optimization problem that enforces multiple, potentially complex constraints of varying importance. We propose Constrained Adversarial Perturbation (CAP), an efficient algorithm that solves this problem using a gradient based alternating optimization strategy. We evaluate CAP across diverse domains including finance, IT networks, and cyber physical systems, and demonstrate that it achieves higher attack success rates while significantly reducing runtime compared to existing baselines. Our approach also generalizes seamlessly to individual adversarial perturbations, where we observe similar strong performance gains. Finally, we introduce a principled procedure for learning feature constraints directly from data, enabling broad applicability across domains with structured input spaces.
Paper Structure (34 sections, 1 theorem, 32 equations, 10 figures, 4 tables, 2 algorithms)

This paper contains 34 sections, 1 theorem, 32 equations, 10 figures, 4 tables, 2 algorithms.

Key Result

Lemma 1

The gradients of the ALF eq:X_simplified_ALF with respect to the dual variables are given by

Figures (10)

  • Figure 1: The dependence of adversarial efficacy of CAPX and baselines over the size of $\bm{X}$ and the $\ell_2$-norm budget is observed. The left columns correspond to the evaluation result over the test set for the LCLD dataset, and the right columns to the IoMT. Subplots \ref{['fig:LCLD_IoMT_asr_vs_T']} observe the effect of size $|\bm{X}|$, \ref{['fig:LCLD_IoMT_asr_vs_l2']} observe the effect of attack radius of perturbation $\lVert{\bm{\delta}}\rVert_2$ over the adversarial efficacy of the universal perturbation. Subplots \ref{['fig:LCLD_IoMT_time_vs_X']} observe the resultant computational cost.
  • Figure 2: $\text{ASR}_\text{Train}$ and $\text{ASR}_\text{Test}$ are ASRs of the universal perturbation over the set $\bm{X}$ itself and unseen test examples, respectively. Time (s) reports total computation cost in seconds. CAPX offers superior adversarial efficacy and requires significantly lower computation time over baselines
  • Figure 3: Summary of average inner product (IP) of a null space vector $\bm{c}$ taken with the normal samples ($\text{IP}_\text{Normal}$) and anomalous samples ($\text{IP}_\text{Anomal.}$) over the training and the test dataset. IP is almost preserved for the normal readings of the test set, signifying its importance as a constraint on the normal readings. On the other hand, the inner product magnitudes rise for anomalous readings across datasets.
  • Figure 4: Summary of adversarial efficacy of individual perturbation when norm budget over $\|\bm{\delta}\|_2$ is fixed to 0.4. In addition to the maximum allowed iteration---common to each method, MoEvA2 includes two more parameters, namely population and offspring size. *T-ms and $\circ$T-ms report time in milliseconds, and they represent the average computational time needed by methods in each step of the iteration. Rows in *ASR report ASR when maximum allowed iteration is fixed to 300 for each method (MoEvA2: population size fixed to 64 and offspring size to 32), and rows in *T-ms report the corresponding average per-step time. CAPx and MoEvA2 are more direct competitors as they both perturb under the feature constraints, unlike PGD. Rows in $\circ$ASR report ASR when the maximum allowed iteration is increased to 625 for both methods (MoEvA2: population size increased to 640 and offspring size increased to 320), and rows in $\circ$T-ms report the corresponding time. Despite operating under the same iteration budget, CAPx, achieves competitive ASR performance and greater time efficiency even when MoEvA2 is configured with larger population and offspring sizes that typically benefit genetic algorithms.
  • Figure 5: Essential Python libraries used in the implementation of the proposed and baseline methods.
  • ...and 5 more figures

Theorems & Definitions (4)

  • Remark 1
  • Definition 1: Feature constraints
  • Definition 2: ASR
  • Lemma 1: Dual gradient